The invention discloses a self-releasing upper pulley with a sliding block. The self-releasing upper pulley with the sliding block comprises a base frame. A rotary shaft is arranged on the base frameand fixedly connected with the base frame. A shaft hole is formed in a rotary plate and connected with the rotary shaft. The base frame and the rotary plate are connected through an unfolding spring.Roller wheels are arranged at two ends of the rotary plate. A control shaft is connected with the rotary plate. A sliding plate is arranged on the right side of the base frame and provided with a rotation stop portion/hooking portion. The sliding plate is provided with a driven surface. A pressing block is arranged above the driven surface. The self-releasing upper pulley with the sliding block isinstalled on an upper door window frame, at the time, the rotary plate does not rotate around the rotary shaft, then a door window is lifted up, a guide rail groove collides with the top end of the pressing block, the driven surface is in butt joint with a driving surface, the sliding plate moves accordingly when the pressing block moves downwards, a control shaft is separated from the rotation stop portion/hooking portion, the rotary plate rotates around the rotary shaft, and therefore automatic releasing is realized. The self-releasing upper pulley with the sliding block is used for a doorwindow accessory.