Summary: By accounting for effects of background noise and signal noise, this paper presents a dynamic model of neuronal oscillator population subject to external periodic stimulation and mixed noise, and introduces the number density to describe the synchronous firing activity of neuronal oscillator population. The numerical simulations indicate that under the background or signal noise, the greater synchronous gain of the neuronal oscillator population is due to the noise enhancement; the smaller synchronous gain of the neuronal oscillator population is due to the reduced noise. As mixed noise, a weak background or signal noise can increase the synchronization of the neuronal oscillator population; the ordered oscillation of the neuronal oscillator population will become disordered. The numerical simulations also show that the gain on synchronization of neuronal oscillator population is more obvious with strong signal noise; the increase of the stimulation frequency will shorten the synchronous oscillation period of the neuronal oscillator population.