WASHINGTON (AP) _ Mayor Marion Barry returned to work Wednesday after more than six weeks of treatment for substance abuse, but top aides said it will be several weeks before he resumes a full schedule.

''He looks good, rested, enthusiastic and very active,'' said Corporation Counsel Herbert O. Reid, a longtime Barry aide. ''He wants to get back to work.''

Barry, who entered Florida and South Carolina substance abuse treatment centers after his Jan. 18 arrest on a drug charge, will be emphasizing continued after-care treatment at the expense of his government duties.

''He will continue to get better, that's a priority,'' Reid said. ''I don't know for sure how long it will be before he resumes his normal schedule, but it will be several more weeks at least, I think.''

Reid and others also said Barry was readjusting smoothly to his office routine.

''We gave him a fairly thorough budget briefing, and he came up to speed pretty quickly,'' one aide said. ''He doesn't seem too far off the mark.''

Throughout the day, top aides were seen entering and leaving Barry's office, many of them carrying budget briefing books.

The city council is set to vote Tuesday on Barry's $4 billion spending package, which includes $210 million in new taxes. A city council aide said the executive and legislative branches are still ''a long way off'' in reaching an accord on the pact.