A stable power system of LTE signal is introduced, the effective value detection technology is adopted to reach high speed real-time sampling, stable power technology of digital pulse is adopted for power control. According to the characteristics of the LTE pulse modulation signal, we use FPGA counter to measure channel delay time；A loop design based on FPGA processing control is given, containing electrically adjustable attenuator, amplifier, coupler detector and modulator; A software algorithm system is designed for the stability of the pulse modulated signal. Experiments show that the power stability control is realized with the error less than 0.5dBm, and the flat power characteristic is guaranteed in the 2GHz~3GHz wide frequency band, the system can satisfy the requirements of wide band, high precision and stable power output.