Abstract: In order to investigate the in sacco dry matter（DM），starch degradability of toasted corns processed with different temperatures and times, 3 health Chinese Holstein lactating cows with permanent ruminal cannulas were selected as experimental animals fed with the diet of concentration forage ratio 55∶45. The result showed that the ruminal degradabilities of toasted corn DM and starch decreased significantly（P<0.05）. Especially the ruminal corn DM and starch degradabilities decreased gradually as the toasting temperature rose and toasting times prolonged respectively. Among all treated groups, the ruminal degradabilities of toasted corn starch for group treated with 140 ℃ 35 min were the lowest, decreased 15.26% compared to control group. The key factors affecting ruminal degradabilities of toasted corn starch were the rapid degrading fractions in toasted corn starch and the degradation rate.