The invention provides an attack method based on active phase compensation of a one-way quantum key distribution system. The safety problem in the active phase compensation of the one-way phase coding QKD system is provided for the first time. The attack method includes linear attach and nonlinear attach. According to the attach method, in the active phase compensation stage, phase information carried by the quantum state sent by Alice is changed by Eve by inserting a phase modulator in a quantum channel and performing selective phase modulation, so that the quantum state is turned into a nonstandard BB84 state; in the quantum key distribution stage, the Eve intercepts the quantum state sent to Bob through the Alice, a measurement operator is selected to perform semi-POVM on the quantum state, and after the measurement result is obtained, a standard BB84 quantum state is sent to the Bob. Under the linear attack, while it can be guaranteed that the ratio of keys 0 to keys 1 is 1:1, the bit error rate generated by the system is lower than a safety value considered by both communication sides, wherein the keys 0 and the keys 1 are received by a Bob end detector.