Abstract: a modulator was designed with 1.8V supply voltage,1.8mW power consumption,16bit precision and figure of merit (FOM) up to 170.Its oversampling rate is 128,using 3 -order noise reshaping.The feedforward structure and one bit quantization were used to reduce power consumption.The PMOSFET was used to achieve local feedback,and improved the performance effectively.The design of the whole circuit and layout was implemented on SMIC 0.18μm process after analyzed the system structure and the submodules such as operational amplifier, comparator and so on.On ss corner,the simulation results show a good performance,the modulator achieved 100. 8dB signal to noise ratio (SNR) in 20kHz bandwidth,and reduced effective bits achieved 16 bits requirement.