Abstract: Songbirds are animal with the ability of vocal learning like human, and the neural basis of vocal learning is similar to the language learning of human. This study investigated the changes in synaptic plasticity of HVC-RA synapses in adult male zebra finches after castration with in vivo electrophysiology technique, analysed the potential functions and mechanisms of androgen in the process of modulating courtship song and song maintaining. The results showed that low frequency stimulation induced short-term depression, high frequency stimulation induced long-term depression in HVC-RA synapses of adult male zebra finches. When the singing was stable after castration, we found that low or high frequency stimulation could not induce long-term or short-term synaptic depression. These results suggested that the stability of singing may depend on HVC-RA synaptic plasticity, and androgens may play an important role in the song stability.