The mixed solutions of soybean protein isolate（SPI） and maltodextrin （MD） were treated by ultrasound. The acid-induced gels were formed by the addition of glucono-δ-lactone （GDL）. The rheological property， microstructure， gel strength and water holding capacity were measured. Effect of ultrasonic treatment on the properties of SPI/MD mixture acid-induced gel was discussed. The crosslinking of protein aggregate could be promoted by addition of MD in SPI due to phase separation， forming more compact and uniform network structure， which resulted in the enhancement of gel network and the shortening of gel time. The ultrasonic treatment would transform the SPI/MD mixture gel from the chain structure to the granular structure， and the granular structure was more obvious with the extension of ultrasonic time. The ultrasonic treatment for 5 min could further enhance the network structure and the ability to resist destruction of SPI/MD mixture gels， and the gel network maintained better structural integrity. However， the ultrasonic treatment for 15 min and 25 min was not beneficial to the establishment of the mixture gel network， and there were large cracks in the microstructure of gels. The integrity of network structure was broken， leading to the decrease of gel strength and water holding capacity.