The principle based on Buck DC-DC converter, starting from the requirements of the system, a high performance error amplifier is proposed. The input of the error amplifier uses bias current cancellation structure, avoiding the influence of the input on the reference voltage; the core circuit adopts symmetrical differential amplifier structure, introducing the structure of positive feedback and negative feedback resistor to improve its performance, and the circuit structure adopts CSMC 0.5 mu m BCD technology. The simulation results show that the trans conductance of the error amplifier is 1.5 mS, the lower limit of common mode can start from 0, the CMRR is 106 dB, the offset voltage is 208.3 mu V, and the power consumption is about 100 mu W, validating the good performance of amplifier.