Abstract: In order to study the influence of fermentation temperature on the quality of yoghurt,the curd time,titration acidity and pH were measured. The fuzzy mathematics method was used to analysis the sensory indicators,and the GC-MS was used to determine the flavor components of yogurt to investigate the effect of 4 kinds of temperature fluctuations on fermentation characteristics and quality of yogurt. The results showed that,fermentation temperature fluctuation in the treatment 1(41 ℃-42 ℃-43 ℃)had no significantly different effects(p>0.05)on the coaglutation time,texture and sensory indexes compared with the control group. Coaglutation time of treatment 2(36 ℃-38 ℃-42 ℃)increased(p<0.05),and hardness,adhesiveness and sensory indexes had no significant difference(p>0.05),but gumminess of yogurt decreased(p<0.05). Treatment 3(42 ℃-38 ℃-36 ℃)had no significantly different effects(p>0.05)on the coaglutation time,adhesiveness,hardness and gumminess of yogurt decreased,and sensory value increased(p<0.05). Treatments 4(42 ℃-46 ℃-48 ℃)and treatment 5(48 ℃-46 ℃-42 ℃)had no significantly different effects(p>0.05)on the coaglutation time,adhesiveness and sensory indexes,but hardness of yogurt increased(p<0.05)and gumminess decreased(p<0.05). There had no significant difference on titration acidity and pH of all treatments. The main volatile flavor compounds in different temperature fluctuation groups were basically the same,but the contents were different. In practical production,the fermentation temperature of yoghurt could not be controlled very precisely which allow small range fluctuation.