In order to improve chromatic dispersion (CD) measurement accuracy and reduce cost, a chromatic dispersion measurement method based on digital phase detector is proposed. The traditional analog phase detector is replaced by an analog to digital converter with low sampling rate and a digital phase detecting algorithm based on all phase fast Fourier transform (FFT), and a particle swarm optimization (PSO) algorithm is applied to the process of curve fitting. High accuracy chromatic dispersion measurement is achieved. The effects of sampling rate, signal noise ratio and FFT length on digital phase detection accuracy are also analyzed. Experiments on verifying the accuracy of the measurement system are carried out. Experiment results show that the accumulated chromatic dispersion uncertainty of G.652 fiber with different lengths at 1550 nm is less than 10 ps/nm, which is better than that of the commercial CD analyzer in metropolitan area network environment.