A prefabricated box girder body concrete automatic conserving device comprises wireless temperature sensors and wireless moisture sensors on the periphery of a prefabricated box girder body. The wireless temperature sensors and the wireless moisture sensors are in wireless connection with a wireless communication module which is connected with a system controller. The system controller is connected with a wireless remote control host which is in wireless connection with a solenoid valve arranged on a diameter-reducing tee part. The wireless temperature sensors, the wireless moisture sensors and the solenoid valve are connected with a mobile power supply through water conservancy project electric cables. A stem line water pipe is connected with a branch line water pipe through the diameter-reducing tee part. The branch line water pipe is connected with a spraying head. The shortcomings that in the prior art, manual watering conservation is used, working amount is large, conservation effect is bad, scientific defecting cannot be carried out, the strength of box girder concrete is directly affected, and structural service life of the box girder concrete is affected are effectively overcome.