To improve the accuracy of digital countering intanstanerous frequency measurement(IFM), a new technology with time frequency converter(TDC) is presented. The measured signal frequency can be obtained by counting the number of the signal in the pulse and using the TDC to measure the pulse width. In FPGA, the basic sequence of frequency measurement is designed, and the control of TDC and the calculation of the data are achieved. In order to improve the stability of the iIFM, the calibration method of TDC is designed, with the measurement of a standard pulse inserted to correct the drift of TDC. The experiment shows that the measurement accuracy of this new method is about 0.3 MHz for the input signal with pulsewidth of 1 μs and the carrier frequency of 1~2 GHz, while the measurement time is less than 1 μs.