Smart meters have been used widespread with the construction of smart grid.The Energy meters are the basis of electricity trading and settlement for power supplier. But unlike tradition meters, smart meters are sensitive to the effects of strong electromagnetic interference because there are many electronic components. Strong electromagnetic environments are not fully established in performance testing. So the high voltage shock device is used for electricity theft which has a strong impact on power supply and safety. Electricity theft mechanism of high voltage shock device is analyzed from some aspects and the improved measures was proposed. The improved smart meter can efficiently solve the issue of electricity theft.