Bird vocalization plays an important role in the ecology and evolution of birds, particularly in passerine birds (songbirds). Like other phenotypes, the vocalization of passerines has shown extensive geographical variations between populations that are isolated by geographical barrier and spatial distance. The relative role of geographical barrier and spatial distance in affecting the variation of vocal variation between populations within species is rarely tested. The Tesia cyaniventer is a small ground-dwelling forest species that distributes between 2000-2800 m in elevation at the Gaoligong Mountains, which is a chain of mountains run from north to south in southwestern China. The western and eastern populations of the Tesia cyaniventer are isolated by mountain peaks above 3000 m, making it an ideal model species to test the relative attributions of geographical barrier and spatial distance to vocal variations between populations. In the breeding season in 2016 and 2018, we recorded and measured 1268 songs of 58 individuals from four populations in the north and south sections of the Gaoligong Mountains, with two sampling sites in each section on east slope and west slope, respectively. We identified 38 song types and 58 syllable types from four populations. Different populations shared few song types in common, while the syllable types shared to a certain extent among the four populations. We measured 11 acoustic traits of each song and compared these traits among four populations. Six of the 11 acoustic traits being measured differed significantly among populations, including lowest frequency (P <0.001), the center frequency (P=0.031), the delta frequency (P=0.008), the introductory syllable frequency (P=0.04), the time interval between the first and second syllables (P=0.001), and the average number of each song (P=0.005). Inter-population comparisons showed that the geographical barrier might have a stronger effect than the spatial distances, although both of them might attribute to variations of song characteristics. Specifically, three acoustic traits showed significant difference between populations with long distance and that are isolated by mountain peak; two acoustic traits showed significant difference between populations only isolated by mountain peak; and only one trait was significant different between populations only affected by geographical distance. Overall, our results showed that the factors affecting the variations might be rather complex, as the mountain barrier and the geographical distance have different isolation effects on acoustic traits of the populations of the Tesia cyaniventer.