In order to solve the task of highly precise and synchronously sampling AC voltage and current for multiple channels, the field calibrator for electric energy meters based on NIOSII has been developed. The overall structure of the system, the voltage sampling module, the current sampling module, the A/D conversion module and the zero-crossing detecting circuit as well as the software developing flow is given. Comparing with traditional implementing strategy of DSP or special metering IC, the design is flexible and offers rapid and accurate performance. The result of test indicates that the system operates stably and accurately.