This study investigated the acoustic variation of songbirds’ vocalization during mobbing event in the sub-alpine forests using playback experiment and automatic acoustic recording (AAR). We played Glaucidium brodiei vocalization and Phylloscopus trochiloides alarm call to induce songbirds’ mobbing behavior and recorded their response vocalizations using automatic acoustic recorders in the Abies-Picea dark coniferous forest in Wanglang National Nature Reserve, Sichuan Province, during the summer of 2021. Altogether 24 experiments were performed on 12 experiment sites, with a total length of 1057 min acoustic recordings, including 12 G. brodiei vocalization experiments, and 12 P. trochiloides alarm call experiments. A total of 28 species of birds belonging to 17 families and 3 orders were observed to participate in mobbing behavior. By analyzing the acoustic indexes of recordings, it was concluded that 1) both G. brodiei vocalization and P. trochiloides alarm call could trigger mobbing event, during which Phylloscopidae and Paridae species were the majority being involved; 2) during playback period, songbirds’ vocalizations are more intense (G. brodiei experiments: SPL_avg=−31.02±4.87 dB vs −42.74±4.68 dB, p = 0.001; P. trochiloides experiments: SPL_avg = −33.26±4.05 dB vs −46.38±4.54 dB, p = 0.001) and less complicated (G. brodiei experiments: H = 0.76±0.02 vs 0.80±0.03, p = 0.001; P. trochiloides experiments: H = 0.77±0.02 vs 0.82±0.02, p = 0.001) than that of pre-playback period; 3) the variability of acoustic indices from pre-playback to during-playback didn’t change significantly between G. brodiei experiments and P. trochiloides experiments. The results provide a new insight into avian behavior studies in the acoustic aspect, and novel behavioral application scenarios for large-scale soundscape monitoring data.