Queen Elizabeth II will send to Washington a touring exhibition of 50 drawings by Leonardo da Vinci. Most of them show horses--horses dignified and violent, horses rearing, walking, galloping, grimacing, fighting, or prancing on parade.

These famous sheets, from the Royal Library at Windsor Castle, will go on view in February 1985 at the National Gallery of Art. The tour was announced on the eve of a state dinner to be given tonight in San Francisco by President Reagan for the royal party.

This is the third major Leonardo show to come to the United States from the queen's unequaled collection of the master's drawings. They were brought to England in the 17th century by Thomas Howard, Earl of Arundel, who had acquired them from a Spanish nobleman.

Other Leonardo drawings--his anatomical studies and his drawings of plants--already have been seen on this side of the Atlantic. But Andrew Robison, curator of prints and drawings and senior curator at the National Gallery, yesterday described the horse drawings as "even more important."

"What makes this group so special," said Robison, "is that it shows such a wide range of dates, styles, media and purpose. Some are drawings done from life. Some are preparatory studies for equestrian statues. Some are sketches for paintings. Some are fantasies. The group includes ink drawings, chalk drawings and drawings done in wash, some in color, some on prepared paper."

Leonardo's horses, through their movements and expressions, display emotions that at times seem almost human. Some roll about in play. Some snarl and bare their teeth as if mad with rage. A few, the most august, seem to be as proud as the warrior saints and military heroes they carry on their backs.

Some are cool and sharply focused, as if they had been drawn with a scientist's detachment. Others have the look of creatures found in nightmares. Some of the most impressive seem almost cinematic. They've been drawn with such freedom, such fluidity and verve, that their hooves appear to flail and their necks to move.

Studies for "The Adoration of the Magi" in the Uffizi Gallery, Florence, for the "Battle of Anghiari," now lost, and for Leonardo's never-completed "Sforza" and "Trivulzio" equestrian statues will be included in the show. So will drawings of other animals--some dragons, a few lions--and on one sheet are shown many cats.

After a three-month showing here, the Leonardo exhibition will travel to the Art Institute of Chicago and to the California Palace of the Legion of Honor, San Francisco, according to Ian M. White, director of the Fine Arts Museums of San Francisco, who made yesterday's announcement.