The invention relates to a slab secondary cooling stepless regulation device. The slab secondary cooling stepless regulation device comprises motors, speed reducers, electric cylinders, hinge shafts, spraying pipes, nozzles, guiding devices, protection plates, fixed protection covers, telescopic protection covers and the like. The motors serve as transmission drive units to output the rotation movement, the speed reducers transmit the rotation movement and amplify the torque, the electric cylinders receive the rotation movement and convert the rotation movement into the linear movement, and the electric cylinders are connected with the spraying pipes through the hinge shafts. The multiple nozzles are arranged on the spraying pipes. The spraying pipes and the nozzles are driven by the motors, the speed reducers and the electric cylinders to move in the output linear movement direction of the electric cylinders, the guiding devices are arranged on the two sides of the spraying pipes, and the guiding direction of the guiding devices is consistent with the output linear movement direction of the electric cylinders. The device has the beneficial effects of being simple in device structure, superior in sealing protection performance, good in stability, high in reliability and practicability, superior in operability and the like. The problem of local over cooling or over heating due to the width change of slabs is systematically solved, and wide market application prospects are achieved.