Abstract: According to the diversification of foreign maps, the vectorization mode based on combination plate map is chosen. The multivocal point and direction information are introduced into the tracing. The combinative use of them not only avoid error tracing and bug in the tracing processing, but also reduce the man machine interaction. The improved algorithm realizes the semiautomatic vectorization of contour line and isobath from the tint area in combination plate map, and the efficient and reliability are proved through experiments.