In this study， pea protein-high methoxyl pectin (PP-HMP) composite particles was prepared by ultrasound， and investigated the effect of ultrasound on the physico-chemical properties of PP-HMP composite particles. Meanwhile， the structure properties of PP-HMP-US were characterized by fourier transform infrared spectroscopy (FTIR)， fluorescence spectroscopy， and transmission electron microscopy (TEM). The results showed that higher emulsifying activity and stability of pea protein-high methoxyl pectin by ultrasound (PP-HMP-US) were observed at 10 min， 5.43 W/cm3 and 15 ℃. Compared with PP-HMP， the turbidity of PP-HMP-US was decreased. Particle size， and PDI of PP-HMP-US was reduced from 1 453.26 nm and 0.34 to 541.44 nm and 0.27， respectively. According to FTIR and fluorescence spectroscopy results， HMP could significantly increased the relative content of β-turn and α-helix from 13.67% and 19.89% to 33.85% and 26.61%， respectively. The addition of HMP inhibited the aggregation of PP， and formed a tighter tertiary conformation. Proper ultrasound treatment of PP could make its β-sheet unfold to form α-helix， and enhance the interaction of PP and HMP. Meanwhile， the exposure of tryptophan residues of PP decreased after ultrasound treatment. In addition， TEM results showed that ultrasound enhanced HMP embedded in PP spherical structure to obtain PP-HMP-US composite particles with more regular and ordered structure. The results provided a theoretical basis for the utilization of pea protein in food processing.