The utility model relates to the density measurement technology for sulfur hexafluoride gas in a smart grid, in particular to a sulfur hexafluoride density measurement apparatus, which comprises a sensor module, a control module, a communication module, WIA (windows image acquisition) wireless sensor network devices and a pressure module. The sensor module is used for acquiring information and connected with the control module. The control module stored with a control program has functions of A/D (analog/digital) conversion, density measuring, input and output, data receiving and transmitting and timed measurement controlling and is connected with the communication module and the sensor module. The communication module sends information to the control module and is connected with a network controller in a WIA wireless sensor network and the control module. The WIA wireless sensor network devices include an upper computer and the network controller, wherein the upper computer is a device for realizing data exchange with the control module by the aid of the network controller. The pressure module is a device for supplying power for the modules in the sulfur hexafluoride density measurement apparatus. The sulfur hexafluoride density measurement apparatus realizes gas leakage detection and remote data transmission and has the advantages of flexibility in installation and arrangement of the wireless network and energy economization.