The invention relates to a phase-locked loop, which comprises a phase discriminator, a filter, a voltage controlled oscillator and an M multiple frequency divider, wherein a reference frequency is inputted by one input end of the phase discriminator, and the output end of the M multiple frequency divider outputs a needed channel frequency; the phase-locked loop further comprises an N/N+1 multiplefrequency divider and an N/N+1 multiple frequency division controller, the N/N+1 multiple frequency divider is arranged between the phase discriminator and the voltage controlled oscillator, one input end of the N/N+1multiple frequency divider is connected with the voltage controlled oscillator, the output end of the N/N+1 multiple frequency divider is connected with the other input end of the phase discriminator, and the other input end of the N/N+1 multiple frequency divider is used to receive control signal generated by the N/N+1 multiple frequency division controller, so that in one working period, the N/N+1 multiple frequency divider can output the multiple of N during the first time period and the multiple of N+1 during the second time period.