The invention discloses a method for measuring critical jet pressure during cutting of dredged clay. The method is characterized by selecting a uniform-strength area, cutting the area by using jet with different strengths through a window cutting manner, measuring the cutting depth, and drawing a fitting straight line according to the change of the cutting depth along the jet pressure, wherein the intercept of the straight line on a jet pressure axis is a critical jet pressure value. The method is capable of reducing consumption of the needed clay samples; the preparation process of the clay samples is complex and has high time consumption, so that the clay can be prepared in one time for multiple experiments; the identity of the characteristics of the prepared clay samples can be ensured; meanwhile, the processes and time for preparing the clay samples can also be greatly reduced.