The special presidential commission studying ways to deploy the new MX missile is expected to recommend to President Reagan that 100 of the big, intercontinental-range missiles be based in existing Minuteman silos, commission sources said yesterday.

The high-powered commission, which was formed in January and is composed of 11 members and eight consultants, is said essentially to have completed its work Friday afternoon after two final days of discussion about how many missiles to recommend.

The sources said that the decision to recommend 100 missiles "was the result, more than anything else, of consultations" with Congress about a level that had a reasonable chance of being approved by lawmakers who have already rejected two Reagan administration plans for MX deployment.

On Wednesday, The Washington Post reported that the commission was "leaning" toward recommending a phased deployment of up to 200 missiles.

Sources yesterday said the higher figure had received considerable attention, especially as a way to improve Reagan's hand in arms control negotiations with Moscow. But Capitol Hill reaction to figures above 100 had been negative, the sources said. They also said there had been discussions of an initial recommendation of 100 missiles while suggesting that more missiles could be added later.

As of yesterday, however, sources said the recommendation would be limited to 100 missiles.

Most officials said it would be recommended that the Minuteman silos be strengthened before the MXs are installed to improve their ability to withstand the shock, heat and radiation of an enemy missile attack. But one official said he was not certain about this.

In any event, the commission will recommend an accelerated program of research and development to see if silos can be strengthened well beyond any initial measures and also to see if a new and much smaller missile than the MX, which would be a less inviting and harder-to-hit target, can be developed.

Sources say the commission, which has held some 30 meetings and heard scores of witnesses, may hold one more session early this week. The final recommendations are expected to go to Reagan within 10 days.