Effect of different physical modification conditions (heating treatment, ultrasound treatment, highpressure treatment, homogenization treatment and microwave treatment) on emulsifying properties and flexibility characterized by sensitivity to trypsin of soy protein isolate was investigated. The correlation analysis between flexibility and emulsifying properties (emulsifying activity and emulsion stability) was also investigated. The results suggested that different physical modification methods had different effects on flexibility and emulsifying properties of soy protein isolate, and emulsifying activity and emulsion stability were increased with the increase of flexibility. The best flexibility and emulsifying activity were got at 121℃ with 10min heating treatment, comparing with other physical modification conditions. Highpressure homogenization treatment had little impact on flexibility but it had great impact on emulsifying activity. Correlation analysis suggested that soy protein isolate flexibility was very significantly and positively correlated with emulsifying activity and emulsion stability under heating and ultrasound treatment conditions, correlation coefficients were 0.969, 0.950 and 0.942, 0.954, respectively. Flexibility of soy protein isolate was positively correlated with emulsifying activity and emulsion stability under highpressure treatment conditions, correlation coefficients were 0.771 and 0.720, respectively. Flexibility of soy protein isolate was very significantly and positively correlated with emulsifying activity and emulsion stability under microwave treatment conditions, correlation coefficients were 0.976 and 0.862, respectively.