The invention belongs to the technical field of underground engineering rock and soil body drilling, cutting and underground engineering disaster prevention and reduction, and provides a magnetic force conversion type intelligent knife changing drilling and cutting device for soft and hard strata. The device comprises a centrifugal mud discharging system, a variable drilling and cutting system, apump water flushing system, a magnetic force conversion system and a framework system. According to the device, the variable drilling and cutting system is utilized to realize rapid drilling and cutting construction of the soft and hard strata; a central drilling bit is arranged in the center of the device to realize ultra-hard soil cutting; a plurality of shell-shaped drilling bits and thread-shaped drilling bits are arranged at intervals around the device to realize drilling and cutting of soft soil, hard soil and homogeneous strata; and the pump water flushing system is utilized to realizerapid discharging of rock debris of any stratum, so that the stratum adaptability of drilling is improved, and the problem of large deviation of hole positions in the drilling construction of soft andhard strata is avoided.