  We establish a Siegel-Weil formula for classical groups over a function field
with odd characteristic, which asserts in many cases that the Siegel Eisenstein
series is equal to an integral of a theta function. This is a function-field
analogue of the classical result proved by A. Weil in his 1965 Acta Math.
paper. We also give a convergence criterion for the theta integral by using
Harder's reduction theory over function fields.
