The invention relates to the technical field of feed processing, and discloses a method for improving the protein solubility of rapeseed cakes; the method includes that the rapeseed cake raw materialis subjected to enzymatic hydrolysis, wherein enzymatic hydrolysis is carried out with the water content of the rapeseed cake raw material in a range of 20-60 wt%. Through the method for improving theprotein solubility of the rapeseed cakes, with the rapeseed cakes as the raw material, the product with high protein solubility can be prepared, and the rapeseed cakes are fully utilized in feed culture industries. The rapeseed cakes have high protein solubility, and are more conducive to absorption and utilization of proteins; the problem of low profits brought by excess production capacity in rapeseed processing industries is effectively solved, and the value-added utilization of the rapeseed cakes in the feed culture industries is realized.