Abstract: Erythritol, mogroside and stevioside were compounded and mixed in 49.5:1:1 to replace sucrose, and the ratio of compound sugar and sucrose under the same sweetness was 7.77:1. The differences of sensory characteristics and physical and chemical indexes between sucrose-free yoghurt with compound sugar and plain yoghurt with the same sweetness sucrose fermented at 43 ℃ were studied. The color, odour and taste of plain yogurt and sucrose-free yogurt were detected by electronic eye, electronic nose and electronic tongue, respectively. The acidity, hardness, viscosity and lactic acid bacteria were determined by phenolphthalein indicator, mass structure, rheometer and plate counting. The results indicated that the acidity range of sucrose-free yogurt with compound sugar and plain yogurt with the same sweetness sucrose ranged from 70.11°T to 72.18°T, and there was no significant difference between them (P>0.05). During the fermentation process, the acid production rate of sucrose-free yoghurt with compound sugar concentration of 4%, 8%, 10% and 12% was faster than that of plain yogurt with the same sweetness sucrose, and the difference was significant (P<0.05). The acid production rate of sucrose-free yogurt with compound sugar concentration of 6% was significantly higher than that of plain yogurt within 1 to 3 h of fermentation (P<0.05), and there was no significant difference in acid production rate between the two types of yogurt within 4~5 h (P>0.05). Within 1 to 3 h of fermentation, the hardness and viscosity of plain yogurt and sucrose-free yogurt with the same sweetness increased slowly. The increasing rate of hardness and viscosity of sugar-free yogurt was significantly higher than that of plain yogurt with the same sweetness (P<0.05). In the fermentation process, lactic acid bacteria proliferation of sucrose-free yogurt with the same sweetness was faster than that of plain yogurt, and there was a significant difference (P<0.05). The sensory score of sucrose-free yogurt was higher than that of plain yogurt with the same sweetness. The odour and color of plain yogurt with sucrose concentration of 4%, 10% and 12% were significantly different from that of sucrose-free yogurt with the same sweetness (P<0.05). The volatile component analysis results showed that 31 and 44 volatile components were detected in different plain yogurt and sucrose-free yogurt, respectively. And there was no significant difference in taste (P>0.05). In addition, there were no significant difference in color and smell between the plain yogurt with sucrose concentration of 6% and 8% and the sucrose-free yogurt with the same sweetness (P>0.05), but there were significant differences in taste (P<0.05). Therefore, plain yogurt was significantly different compared to the equivalent sweet sucrose-free yogurt.