The invention discloses a Q-switching laser for improving Q-switching performance, and relates to the laser field, solving the problem that an existing Q-switching laser is wide in the laser pulse and low in the Q-switching efficiency. The Q-switching laser comprises a totally reflecting mirror 1, a 90DEG polarization rotation electro-optical switch, a laser gain medium, a polarizing film, an electro-optical Q-switching switch, an output mirror, a totally reflecting mirror 2 and a pumping source, wherein when the electro-optical Q-switching switch is quickly back to 0 and the 1/4 voltage is quickly applied to the 90DEG polarization rotation electro-optical switch at the same time, the laser inverted population corresponding to a pumping threshold value of a laser resonant cavity is reduced to half of a common Q-switching laser and the difference between the laser inverted population and the laser inverted population corresponding to the pumping threshold value of the laser resonant cavity is increased, so that giant pulse laser output is realized. The Q-switching laser for improving Q-switching performance has the advantages of being narrow in the laser pulse and being high in the Q-switching efficiency.