Objective To investigate the contrast effects of phacoemulsification on hard nuclei with torsional mode and burst mode.Methods Fifly-one cataract eases(65 eyes)with nuclei density grade of Ⅳ (according to the Emery classification)were comprised in this study.All cases were randomly divided into two groups:torsional group and burst group.The ultrasound time(UST)and cumulative dissipated energy(CDE),corneal edema,best corrected visual acuity(BCVA)and corneal endothelial cell loss were recorded.Results The mean CDE in torsional group was statistically significantly lower than that in burst group(P<0.05).The difference between the two groups was not statistically significant(P<0.05).Cornea edema on the first postoperative day in torsional group was statistically significantly better than that in burst group(X2=8.620,P<0.05),but on the seventh postoperative day,there were no statistically significant differences between the two groups(X2=0.955,P>0.05).The average best corrected visual acuity in torsional group was statistically significantly better than that in burst group on the first postoperative day(X2=4.975,P<0.05),but on the seventh and thirtieth postoperative day,there were no statistically significant differences between the two groups(P>0.05).The mean endothelial cell loss in torsional group was significandy less than that in burst group on the third postoperative month(t=4.317,P<0.05).Conclusion The intraoperative damage to oeular structures may be miuimized and the level as well as the rapidily of visual rehabilitation may be maximized with the torisional mode during phacoemulsification on hard muclei of cataract surgery. Key words: Phacoemulsification; Hard Muclei; Torsional mode; Burst mode