The utility model provides a device for producing large-grained ammonium persulfate crystals. The device comprises a crystallization kettle; a coil pipe and a stirrer are arranged in the crystallization kettle; the stirrer is located below the coil pipe, and a main shaft of the stirrer is connected with an output shaft of a speed reducer; the speed reducer is controlled through a frequency-variable speed governor; the outlet end of the crystallization kettle is connected with the inlet end of a centrifuge; a liquid outlet of the centrifuge is connected with a production system; a discharge port of the centrifuge is connected with the inlet end of a dryer; a cooling jacket is arranged outside the crystallization kettle; one end of the coil pipe is connected with a water inlet pipe, and the other end of the coil pipe is connected with a water outlet pipe; and the upper part of the jacket is provided with a freezing brine outlet, the lower part of the jacket is provided with a freezing brine inlet, and a valve is mounted at the freezing brine inlet. According to the device for producing large-grained ammonium persulfate crystals, technologies, such as stepped cooling, frequency variable control and the like, are fully utilized according to the crystallization characteristics of the ammonium persulfate crystals, so that the large-grained ammonium persulfate crystals meeting the market demand can be produced.