During breeding season, from May to August 2017, we collected songs from 80 breeding males of Dusky Warbler (Phylloscopus fuscatus) in Saihanba, Hebei Province. The changes of song types, song parameters and song syllable types were analyzed. There were two sentence patterns in the song of the males: S-song (Fig. 1a) and V-song (Fig. 1b). There were significant differences in the song output of S-song and V-song among months (ANCOVA: F3,75 = 17.983, P < 0.05; F3,75 = 17.983, P < 0.05; Fig. 3), with more S-song used than V-song in the whole breeding season. The output of S-song and V-song in each month showed the opposite trend, with relatively more output of S-song in early (May) and late (August) breeding season, and more output of V-song in the middle breeding season (June). There was significant difference in the maximum frequency (ANCOVA: F3,75 = 4.841, P < 0.05; Table 1), bandwidth (ANCOVA: F3,75 = 3.814, P < 0.05; Table 1) and peak frequency (ANCOVA: F3,75 = 3.793, P < 0.05; Table 1) among months. Based on the 2 400 song verses from 80 males, 65 syllable types were obtained (Fig. 4). More than 80% of the syllable types were used in all months (Fig. 5), but the number of syllable types used in each month were significantly varied (ANCOVA: F3,75 = 5.456, P < 0.05; Fig. 6). The peak of syllable diversity was in July, with 19.79 ± 3.69 syllable types used, there were fewer syllable types used in May and August, with the least in August.