Abstract: Activity of the catalysts with Ce↓0.75Zr↓0.25O↓2 as the addition agent was evaluated.The results showed：there was scarcely any difference between Ce↓0.75Zr↓0.25O↓2 solid solution prepared by solid-solid chemical reaction and that of by traditional  co-precipitation method as the catalytic addition agent in three-way catalyst.They both have good effect on purification of analogous auto-exhaust.Moreover the effect of Ce↓0.75Zr↓0.25O↓2 on Cu/CeTi-PILC catalyst when propylene selectively catalyzed NO was studied.The results indicated that Ce↓0.75Zr↓0.25O↓2 solid solution could improve catalytic activity by 5% of Cu/CeTi-PILC to C↓3H↓6 and NO，light-off temperature of C↓3H↓6 drops 15 ℃，and that of NO drops 112 ℃.