Abstract: A certain type of turbocharged unit can easily surge when it is operated under a low load. This study is based on an analysis of the mechanism of turbocharged unit surge, identifying the surge boundary parameter using Differential Evolutionary(DE) algorithm, and using the residuals of actual test data and theoretical calculation results to correct errors, which avoids the deviation caused by using the experiential value or experimental data under an ideal state as the identification. Studying the characteristics of turbocharged unit surge under low load is based on the obtained surge boundary curve and the existing turbo charging model. The relationships between the compressor rotor speed, pressure ratio, air flux, minimal opening and bypass baffle air flux were obtained through simulation experiments. The results show that the unit must be restarted when the rotor speed of the compressor is under 8.35% of the rated speed; the surge will disappear when the rotor speed of the compressor exceeds 20.37% of the rated speed, and the safe opening of the bypass baffle that corresponds to the rotor speed of the compressor should be kept up when the rotor speed is between 8.35% and 20.37% of the rated speed.