Taking the crucian carp as the research object, the tolerance to different depressurization rates under high water pressure conditions is explored by experimental investigation with the variable-controlling method and the statistical analysis method. The effects of water pressure changes on crucian carps and the pressure tolerance difference of individuals of various sizes are analyzed. The results show that two closely related factors, initial pressure and the depressurization rate, both have obvious effects on the health of crucian carp. Generally speaking, the crucian carps stay uninjured under the pressure within 3 MPa; when the pressure comes within the range of 4-10 MPa, the greater the pressure and the depressurization rate are, the more likely the carp gets injured; the crucian carp will die under the pressure exceeding 10 MPa, and the greater pressure results in the decline of the death depressurization rate threshold. In addition, it is found that the crucian carp tolerance to the pressure change does not seem to have any significant relationship with their individual size. The research is expected to provide some theoretical basis and guidance significance for deepwater aquaculture and deepwater fishing technology in the future high-tech oceanic fishery.