The invention relates to a pressure equalizing device of fixed spraying systems, and the device comprises a conical shell, a float switch, a regulating spring, a nozzle and a bracket. The nozzle and a water inlet pipe are connected by virtue of the conical shell; the regulating spring is arranged at the bracket which is positioned at the bottom of the inner side of the conical shell; the float switch is connected with the regulating spring and can slide back and forth along a guide rail which is fixed between the top in the conical shell and the bracket at the bottom in the conical shell; in order to reduce the incoming flow impact loss, the upper tip part of the float switch is arc-shaped. By adopting the conical shell, the float switch and the regulating spring of different sizes, the device can be matched with the nozzles of various fixed spraying systems for use so as to uniformize the pressure and speed of the inlet of each nozzle. When the pressure and speed of the nozzle inlets are the same, the water sprayed by the nozzle can be the same in flow and spray radius so as to achieve the aim of equalizing the water distribution.