President Reagan has converted all his investments except his two California houses into two certificates of deposit totaling $740,000 which will be placed in a blind trust in compliance with the Ethics in Government Act.

White House deputy press secrtary Larry Speakes said yesterday that the trust arrangement was accepted Wednesday by the act's administrators.

Reagan's net worth appears to be about $3.75 million. In addition to the securities, his Pacific Palisades house is being offered for sale at $1.9 million and his 688-acre ranch near Santa Barbara is valued at slightly more than $1 million.

The trustee selected by Reagan to watch over his assets for the duration of his presidency is Raymond J. Armstrong, president of a New York investment firm, Starwood Corp. Once Armstrong becomes the trustee, he will be obliged by law not to disclose what investments he is making on Reagan's behalf to the president or to anyone else.

The purpose of the ethics act, which was passed after Watergate, is to avoid potential conflicts of interest or the appearance of such conflicts.

The only information Reagan will receive about his assets will be periodic reports on their value.

At the moment, he owns two certificates of deposit at the Bank of America. One is worth $540,000 at an interest rate of 17.25 percent and matures Feb. 9. The second is worth $200,000 at 16.875 percent and matured yesterday.

Reagan intends to put some or all of the proceeds from the sale of his Pacific Palisades house into the blind trust, Speakes said. The president appears to face a large capital gains tax on that sale. He built the house for $25,000 in 1956.

The White House also announced yesterday that, responding to an appeal from Atlanta Mayor Maynard Jackson, Reagan has sent two Justice Department officials to help in the investigation of murders of black children in that city.

"The children of Atlanta are under attack," Jackson said in a telegram to Reagan describing the murders of 14 black children and the disappearance of three others over the last 18 months.

Vice President Bush telephoned Jackson Thursday evening to tell him that Charles Renfrew, deputy attorney general, and Ken Starr, counselor to the attorney general, would be sent to make contact with Atlanta officials about the murders.

At his Thursday press conference, Reagan cautioned that there may be little the federal government can do except possibly under civil rights statutes, since federal crimes may not be involved. "Yet we want to be helpful because that is a most tragic case," Reagan said.

In another action, Reagan accepted the resignations of John Sawhill, chairman of Synfuels Corp., and its other four directors.

White House press secretary James S. Brady said he expects Reagan will nominate and submit to the Senate other candidates to head the corporation, but at salaries well below the levels established by the Carter administration. Sawhill was to be paid $175,000 annually. The other resigning directors are John deButts, Catherine Cleary, Lane Kirkland and Frank Savage.

President and Mrs. Reagan left the White House in midafternoon for their first visit to the presidential retreat, Camp David.

Before leaving, Reagan held a series of meetings with Republican and Democratic members of Congress on the economic proposals he is putting together for submission to Congress in mid-February.

Brady was asked whether the administration is having problems finding women qualified for sub-Cabinet jobs. Only a handful of women have been named to senior administration posts. Brady said the Reagan administration "certainly can and will" find qualified women.