Abstract: Dewatering of soybean food is a very crucial step. Attaching a weight is used in the dewatering process traditionally, whose efficiency is low. Recently people found that electroosmotic dewatering is an effective way. However, many factors influence the efficiency practically. In order to get a satisfying result, further study is necessary. The dewatering efficiency was improved by using the method of different pulse-time ratio electric field on tofu. The effects of voltage and positive (negative) electric fields on the dewatering efficiency were discussed. The series of results indicate that in a certain range the dewatering efficiency increases with the increasing voltage of electric field. Furthermore, the electric field will restrain the sample of the joints from changing color to some degree, which indicates that a best pulse-time ratio exists.