In terms of operating condition in distribution system，a system based on GPRS networks is put forward by taking a practical monitoring system of distribution transformer as an example. The structure and operational principle of electricity stealing prevetion of this system is introduced in detail. It is pointed out that ,by using the real－time characteristics of monitoring system of distribution transformer to develop the function of electricity larceny prevention is much better in fast larceny scout and real time alarm than in kilowatt－hour meter. This system has many functions，such as transformer supervision， measuring , communication , etc. This new system，which is characterized by little investment and convenient management, especially suitable for the improvement project of the distribution system.