The present invention discloses a pet litter box, comprising: a base, a litter tray detachably installed in the base, an upper shell detachably connected to the base or the litter tray, a baffle grate is connected to the upper shell for sifting litter particles and litter clumps, a driving assembly detachably connected to both sides of the litter tray for driving the litter tray to rotate, thereby sifting the clean litter particles into the space formed by the baffle grate, the upper shell and the litter tray, while the litter clumps are sifted outside the baffle grate and into the waste bin; The bottom of the base is detachably connected with several supporting feet and a waste bin for storing litter clumps; when stored, the upper shell, the driving assembly, the supporting feet, and the waste bin all fit entirely within the litter tray.