In order to explore the effects of different ultrasonic powers pretreatment and mass fraction of Inonotus obliquus polysaccharide (IOP) on the properties and structure of composite gel of Inonotus obliquus polysaccharidehemp protein isolate, the particle size and rheological properties of hemp protein isolate (HPI) gels were measured under different ultrasonic powers pretreatment. After determining the optimal ultrasonic power, the effect of adding polysaccharide on the water holding capacity, texture, rheological properties and electrical potential and protein molecular conformation of the composite gels were investigated. The results showed that ultrasonic pretreatment at 300 W for 10 min could reduce the particle size of the HPI gel and improve its rheological properties. The water holding capacity, hardness, and elasticity of the composite gels increased after adding 1.00% IOP. The α-helix and β-turns of the protein were transformed into β-fold and irregular curls, and the absolute value of the electrical potential increased. In conclusion, ultrasonic pretreatment at 300 W for 10 min and addition of 1.00% IOP could enhance the performance and network structure of composite gels, which provide a theoretical basis for the application of IOP in plant protein systems.