Based on the theory of hydraulic self-reversing and pressurization, a variable cross-section squeeze pulse water jet rock breaking platform was built. When the nozzle diameter is 0.5 mm, the granite erosion and crushing experiments under different driving pressures are carried out, and the depth, volume and specific energy consumption of the erosion pit are analyzed. The results show that the device can achieve intermittent injection after pressurizing the input fluid at a rate of 5.8 times. Meanwhile, the pressurization process of fluid is divided into ascending section, stable section and descending section. Compared with the continuous water jet with the same peak output pressure, the depth of destroyed granite is increased by 129 %–288 %, the volume of broken granite is increased by 37 %–121 %, and the specific energy consumption per unit of crushing volume is reduced by 21 %–74 %. The device can use low-pressure fluid to effectively crush granite.