The vanguard of the Republican National Convention assembled yesterday to draft a 1980 campaign platform and celebration a foregone conclusion: the nomination of Ronald Reagan.

The show was orchestrated for harmony as the GOP sought to contrast its solidarity with the contention still facing the Democrat.

Potential points of Republican friction seemed to evaporate in advance.

Former secretary of state Henry A. Kissinger, who was scheduled to speak before platform drafters today, abruptly canceled his appearance.

A spokesman for Sen. John G. Tower of Texas, the platform chairman, said Kissinger blamed personal commitments for his withdrawal.

Conservative Republicans have long been critical of Kissiner, and Reagan is certainly no fan. In 1976, he forced language sharply critical of the then-secretary of state into the platform run upon by Gerald R. Ford.

Tower said Kissinger had reservations about testifying because he did not want to take the edge off his major convention speech next week. Tower said he was disappointed Kissinger will not address the committee.

A compromise was likely to avoid a platform dispute over the proposed Equal Rights Amendment. Campaigning for the nomination, Reagan repeatedly declared his support for equal rights for women but said he was opposed to the constitutional amendment. The platform may skirt the ERA dispute in much the same way.

It will, after all, be Reagan's platform. He is unchallenged for the nomination, and his delegates are in full command of the proceedings. The 106-member platform committee held its first session late yesterday, a closed-door organizational meeting. Today the committee hears addresses from Michigan Gov. William G. Miliken, economist Arthur Burns, former secretary of state Donald Rumsfeld and Rep. Guy Vander Jagt of Michigan.