The measurement-device-independent quantum key distribution (MDI-QKD) can remove all detector side-channel attacks, which greatly boosts the practical application of the quantum key distribution. However, this protocol still has a strict assumption that the states in source side must be perfectly prepared. The imperfections of the modulators in source side would bring side-channels and threaten the practical security of the system. To protect against state-preparation imperfections, the uncharacterized-source MDI-QKD, which can still generate secret keys when the prepared states are uncharacterized, have been put forward. This protocol is a great combination of the theoretical information security and the practical security. Through the three-intensity decoy state method and the self-developed Sagnac-Asymmetric-Mach-Zehnder coding structure, the measurement device-independent quantum key distribution system without characteristic source is successfully built, and the secure key distribution rate of 1.91×10 ^-6 is achieved under the fiber channel of 50.4 km and the repetition rate of 25 MHz.