How to estimate the randomness of the measurement outcomes generated by a given device is an important issue in quantum information theory.Recently,Brunner et al.[Phys.Rev.Lett.112(2014) 140407]proposed a prepare-and-measure quantum random number generation scenario with device-independent assumption,which indicates a method to test the randomness of bit strings according to the generation process rather than the results.Based on this protocol,we implement a quantum random number generator with an intrinsic stable phase-encoded quantum key distribution system.The system has been continuously running for more than 200 h,a stable witness W with the average value of 0.9752 and a standard deviation of 0.0024 are obtained.More than1 G random bits are generated and the results pass all items of NIST test suite. How to estimate the randomness of the measurement outcomes generated by a given device is an important issue in quantum information theory. Recently, Brunner et al. [Phys. Rev. Lett. 112 (2014) 140407] proposed a prepare-and-measure quantum random number generation scenario with device-independent assumption, which indicates a method to test the randomness of bit strings according to the generation process rather than the results.Based on this protocol, we implement a quantum random number generator with an intrinsic stable phase-encoded quantum key distribution system. The system has been continuously running for more than 200 h, a stable witness W with the average value of 0.9752 and a standard deviation of 0.0024 are obtained. More than 1 G random bits are generated and the results pass all items of NIST test suite.