Abstract: Polystyrene/poly(ethylene terephthalate-co-1,4-cyclohexane dimethanol terephthalate) (PS/PETG) blends and PS/modified PETG blends were prepared by torque rheometer. The rheological properties of PS,PETG,and modified PETG were tested by using rotational rheometer and melt flow rate tester；the morphology structure of blends were investigated by using scanning electron microscope. The result showed that average particle size of PETG in PS/PETG blends and modified PETG in PS/modified PETG blends were increased with the PETG and modified PETG content increasing, the particle density showed crosscurrent; when the content of modified PETG and PETG was the same,the average particle size of modified PETG was high than the PETG,and the particle density of modified PETG was less than PETG，the particle size distribution of modified PETG was narrow.