A novel reading out circuit (ROIC) of AlGaN ultraviolet detector is proposed. The ROIC consists of analog circuit and digital circuit. The analog circuit includes integrating amplifier, sampling-hold circuit, buffers and output drivers. The digital circuit gives the ROIC extra functions. In this paper, the theoretical analysis and simulation results of the circuit are given. A chip is designed by using the 0.35μm 2P3M CMOS processes. Dimension of the chip is 11.8mm×11.1mm. The measurement and analysis of the main parameters are implemented successfully and the ROIC’s function is verified.