Abstract: The new spline snbdomain method is advanced to analysis the straight continuous box girder bridge with variable crosseetion but constant height by this paper. This method based on the B₁,B₃ spline and the variation principle, possesses high approach accuracy, less calculation, and suit for analysis of the bridge with various support condition under various load condition. Especially for common box girder adopted in engineering design, its static analysis may be performed in microcompufer.