Tunnel boring machine (TBM) faces the problems of difficult rock breaking and high cutter loss when excavating hard rock, leading to low boring efficiency and high construction cost. In order to improve the rock-breaking performance of TBM cutterhead, various new auxiliary rock-breaking technologies have attracted much attention, among which water jet assisted rock-breaking has great potential. The disc cutter rock breaking experimental device with the function of water jet cutting slit is used to study the effects of single slit and double slit assisted cutter breaking. It is find that there exists the law of "critical spacing", and based on this law, the load models of single and double slit assisted cutter breaking have been established; A method of arranging water jet nozzles on TBM cutterhead is proposed. Based on this, the tilting moment, radial force, thrust force and torque calculation models of the cutter are established. The resluts show that: The load models based on the critical spacing ratio S/S_max can reflect the load reduction and change rule of cutter and cutterhead, and it can be used as a reference calculation method for the load of water jet slit-assisted rock breaking and water jet TBM cutterhead load.