Abstract: Based on the two-fluid model, the dispersion relation of ion temperature gradient (ITG) mode and trapped electron (TE) mode was analyzed theoretically. Based on Weiland model, the effect of collision on the growth rate of ITG mode and TE mode was studied with the consideration of ion parallel velocity and TE. The calculation result based on HL-2A shows that the growth rate of ITG and TE modes in core plasma is closely related to perturbed wave number. Moreover, the growth rate of ITG mode is proved to decrease in the presence of magnetic shear.