The invention discloses a thread transmission type adjustable rear wheel locking device for roller skates. The thread transmission type adjustable rear wheel locking device comprises a fixed frame, arotary thread rod, a locking block and an adjustable nut, wherein the fixed frame is downward provided with corresponding fixed parts; the rotary thread rod is rotatably and horizontally mounted between the two fixed parts; the locking block can be mounted between the two fixed parts in a manner of sliding up and down; friction surface, which are pressed on a rear wheel and are used for locking the rear wheel, are arranged at two sides of the locking block; a straight groove is formed in the upper end along the axial direction of the rotary thread rod; inclined sliding grooves are correspondingly formed in two side walls of the straight groove; the adjustable nut is matched and twisted on the rotary thread rod; a sliding block, which is connected with the adjustable nut and corresponds andinclines to the sliding grooves, is arranged below the adjustable nut; two side ends of the sliding block are inserted into the sliding grooves formed in the two side walls of the straight groove respectively. By adopting the thread transmission type adjustable rear wheel locking device, a stepless adjustment function is realized; the device can be suitable for the rear wheels with different sizes; the locking stability of a sliding wheel is better and the safety is improved.