The invention discloses a method for realizing the group interval-adjustable output of sub pulses through a multi-step pump, and a laser. The laser comprises a total reflective mirror, a laser medium,a passive Q-switched crystal, an output mirror, a pumping source, a laser power supply and a multi-step controller. The total reflective mirror, the laser medium, the passive Q-switched crystal and the output mirror form a laser resonant cavity and are sequentially arranged in the light path direction of the laser. The pumping source and the laser medium are arranged up and down to form a pumpingmodule part. The pumping source, the laser power supply and the multi-step controller form a pumping light control part which is sequentially arranged from top to bottom. According to the scheme, theheight of each step and the width between every two steps in the multi-step controller are controlled. By utilizing the saturable absorption characteristic of the passive Q-switched crystal, the pulse group laser output with adjustable sub-pulse intervals is obtained. The technical problems that the pulse interval of conventional passive Q-switching laser is uncontrollable, and the Q-switching energy is not equal due to the change of the pulse interval during active Q-switching are solved.