ANCHORAGE, Alaska (AP) _ Secretary of State George P. Shultz, heading to China, said Thursday that the Iran-Contra affair will not impede U.S. foreign policy, including its efforts to prevent China and other countries from selling arms to Iran.

Shultz, who left Washington before a presidentially appointed commission released a lengthy report on the Iran-Contra matter, told reporters he had not read it and was unable to comment.

No consideration was given to delaying the long-scheduled trip to China, he said, although he tried without success to obtain a sealed copy of the report to be opened after his departure.

''I would prefer to be'' in Washington to meet with President Reagan after the commission, headed by former Texas Sen. John Tower, presented its report, he said.

''On the other hand, the Tower commission changed its date, and I think that my course of action is to follow the president's instructions...to get on about my business ... conducting the affairs of the secretary of state energetically,'' he said.

As he has since the Iran arms sale was disclosed last November, Shultz said he wished he had done more to stop them, but he will not resign.

''I have said that I don't give myself very high grades in all of this,'' said Shultz, who is a professor on leave from Stanford University.

''As far as my own position is concerned, I don't have any plans to leave, so you can wipe that off your slate,'' he said.

''It's such a pleasure to be on a trip so I can stop testifying and rushing around from one thing to another and concentrate on one area,'' he said.

Shultz, in a news conference aboard his Air Force jet, said no diplomats from China or any other nation had told him that the clandestine arms sales to Iran had hampered American efforts to curb the flow of weapons to Iran and Iraq in order to force an end to the conflict.

''They may have thought about that, but they haven't said it to me,'' he said before his plane touched down in Anchorage to refuel.

''Our credibility is not weakened,'' said Shultz, saying he would raise U.S. concern about arms sales when he meets with the leaders of China, which has emerged as the leading weapons supplier to Tehran.

Shultz and his party were to cross the international dateline later Thursday, thereby missing Friday, and to spend Saturday in Hong Kong before beginning a six-day tour of China with a visit to scenic Guilin.

Shultz declined to spell out what he hoped to accomplish over the remaining two years of the Reagan administration, but he said ''we have a full agenda'' in relations with China and the rest of the world.

Despite repeated questions on any new U.S. policy initiatives, Shultz was unable to mention any new idea for arms control or bringing peace to the Middle East and Central America.

Shultz said that in meetings with Chinese leaders next week in Peking, he will express concern over their human rights policies, especially the recent expulsion of two American journalists, John Burns of The New York Times and Lawrence MacDonald, a U.S. citizen employed by Agence France Presse, on vague espionage charges.

''The first thing is the expulsion of journalists. There have been two now,'' he said. ''That's a matter always of concern to us, given our views about the importance of freedom of the press ....''

And Shultz said he will ask them whether a recent crackdown on China's democratization movement will slow introduction of free-market principles into the Chinese economy.

''I will be very interested in what they have to say to me about internal developments in China,'' he said.

''I think it is a very interesting period, actually, if you look around the world and see ... how each society has some combination of attention to the freedom of expression and the degree to which that is constrained,'' Shultz said.

''We know that when a society that is moving in that direction from a different tradition does so, that's a hard thing to do,'' he said.

Chinese officials, including Deng Xiaoping, say that ''their policy (of economic reform) continues, so ... one reason to go is to listen to the Chinese leaders and get a sense of how they express it to me,'' he added.