For the first time President Reagan has named a Hispanic-American to a Cabinet post, in an apparent bid to woo the important Hispanic vote for George Bush.

Lauro Cavazos, 61-year-old president of Texas Tech University, would replace departing Education Secretary William Bennett, whose resignation is effective on Sept. 20."This is a proud day, not just for Hispanics and Hispanic-Americans - it's a proud day for all Americans," the president said in announcing the nomination.

Hispanic voters make up significant parts of the electorate in such key states as Texas and California. Bush has already promised he would name a Hispanic to his Cabinet, a pledge political analysts viewed as helpful in the Southwest.

But Reagan, who told reporters he had consulted Bush on the nomination, dismissed suggestions the naming of Cavazos was aimed more at helping the vice president in the fall election than carrying out his own policies. "No, I'm just still working at the job here," he said.

Cavazos, who has a doctorate in physiology and teaches anatomy, requires Senate confirmation to succeed Bennett.

Bennett, one of the administration's most conservative and colorful Cabinet members, made headlines with scathing criticisms of American educators. He said in May he wanted to leave his post in September.

A fifth-generation Texan, Cavazos is the son of a foreman on the King Ranch in south Texas, said to be the largest in the nation.

After serving in the army in 1945-46, he graduated from Texas Tech University in Lubbock with a degree in zoology. He earned a master's in zoology from Texas Tech in 1951 and a doctorate in physiology from Iowa State University in Ames in 1954.

From 1954 to 1964, he served in various teaching positions at the Medical College of Virginia and from 1964 to 1980 as professor of anatomy at Tufts University School of Medicine in Massachusetts.

He was dean of medicine at Tufts from 1964 to 1980 when he took over the presidency of Texas Tech.

He has published numerous papers on anatomy and medical education and has been particularly active in trying to find solutions to the high school dropout rate among Hispanics.

Married to the former Peggy Ann Murdock, Cavazos has 10 children ranging in age from 21 to 31.

Cavazos was described by friends as a political moderate and was praised by Hispanic leaders.

Jose Garcia DeLara, national president of the League of United Latin American Citizens, said Cavazos was "eminently qualified" for the post.

"He's a pillar of strength in the community in Texas. "We have nothing but great praise for him," DeLara said.