The present disclosure proposes a flow guide device for a discharge cavity having a symmetrical configuration and including two pairs of electrodes; the flow guide device comprises two rotors which correspond to one pair of the two pairs of electrodes, respectively, installed positions of which are symmetrical about a symmetrical plane of the discharge cavity and is beneath the electrodes, a rotational axis of which is parallel to an axial direction of the electrodes which is parallel to a base plane of the discharge cavity, and the two rotors have opposite rotation directions and identical rotation speeds. The flow guide device further comprises a spoiler plate and a flow guide plate so that the discharge gas flow passes through the discharge cavity in a manner of high speed and uniform cycling when flowing through the discharge region. Thus, the discharge quality is guaranteed so as to improve the energy and reliability of the laser.