The 150th anniversary of Texas' declaration of independence from Mexico is remembered by a commemorative being issued today in San Antonio.

The Republic of Texas won its independence on the battlefield and remained an independent republic for nearly 10 years before becoming the 28th state.

Today's first-day-of-issue ceremony is being held at San Antonio's downtown post office, just north of the Alamo, the symbol of the Lone Star State's war for independence in 1836. James Michener, author of the current best seller "Texas," is the principal speaker.

* The lone star of the Republic of Texas, which was incorporated into the state flag, is one of the focal points of the new stamp. Another is a silver spur, said to have belonged to Antonio Lopez de Santa Anna, the Mexican military leader who was defeated in the decisive battle of San Jacinto, which brought independence to Texas.

The new stamp is the second for the Republic of Texas. In 1936 its centennial was marked by a 3-cent commemorative that had at the left a cameo portrait of Sam Houston, the victorious American general and the first president of the republic, and at the right another cameo of Stephen Austin, who with his father, Moses Austin, established the first American colony of several hundred families in Texas. They flanked a drawing of the Alamo.

The new stamp, a vertical, has been produced by gravure in red, black and blue. The design is the work of Don Adair of Richardson, Tex.

There is a three-digit plate number per post office pane of 50 stamps, preceded by the letter "A" to denote private printing. The stamps were printed and formed into sheets at the J.W. Ferguson plant in Richmond. The sheets were then sent to the American Bank Note Company in Chicago for perforation and processing into post panes.

Collectors of first-day-of-issue cancellations have the usual 30-day grace period from the issue date to place the orders, which must be postmarked no later than April 1, and alternative ways of ordering.

Collectors affixing stamps themselves on their addressed first-day covers should send them to Customer-Affixed Envelopes, Republic of Texas Stamp, San Antonio, Tex. 78284-9991.

Collectors preferring full processing by the Postal Service should send their addressed envelopes, with 22 cents per stamp to be affixed, to Republic of Texas Stamp, Postmaster, San Antonio, Tex. 78284-9992. Personal checks are accepted.

The following stamps, with their first days of issue, are scheduled this month by the United States, the United Nations and Canada.

United States -- March 19: William Jennings Bryan $2 regular issue, Salem, Ill. 62881; March 21: Commemorative stamp booklet of five 22-cent stamps for fish in American waters in two panes, Seattle, Wash. 98109.

United Nations -- March 14: Three commemoratives for the U.N. Development Program and one 5-cent regular issue. U.N. Postal Administration, Box 5900, Grand Central Station, New York, N.Y. 10017.

Canada -- March 7: For Vancouver Expo '86, 34- and 68-cent stamps; March 14: a $5 regular issue for Mauricle National Park. Philatelic Service, Canada Post, National Philatelic Center, Antigonish, N.S., Canada B2G 2R8.