Abstract: The objective of this trial was to study the effects of different DCAB on the production performance, blood chemistry and lymphocyte apoptosis of heatstressed beef cattle. 30 Simmental cattle with similar weight( (450±10)kg) were randomly divided into three groups，every group contains ten cattle. The diets of three experimental groups was group Ⅰ(control group, DCAB, 108 meq·kg-1 DM), group Ⅱ(228 meq·kg-1 DM ), group Ⅲ（347 meq·kg-1 DM）. The results showed that, under the condition of heat stress, different DCAB value in diet didn’t influence rectal temperature, while the respiratory rate decreased linearly with increasing DCAB (P<0.05) . Compared with control group, daily weight gain of beef cattle in group Ⅱ and Ⅲ increased 29% (P<0.05) and 25% (P<0.05), respectively, feed conversion（feed/gain）decreased by 17.34% (P<0.05) and 11.46% (P>0.05), respectively. With the increasing DCAB, dietary NDF and ADF apparent digestibility improved (P>0.05), Ca, ash apparent digestibility showed quadratic change, crude protein and crude fat apparent digestibility had no significant difference. Compared with the control group, serum T4 levels of groupⅡ and group Ⅲ were increased 58.1% (P<0.05) and 31.9% (P>0.05), respectively, SOD levels increased 18.98% (P>0.05) and 48.18% (P>0.05 ), respectively. Increasing DCAB had no significant effect on serum glucose and urea nitrogen, albumin. Increased DCAB could significantly reduce lymphocytes early apoptosis (P<0.01), late apoptosis (P<0.01) and total apoptosis rate (P<0.01), reduce the proportion of lymphocytes (P<0.05) in peripheral blood of beef cattle, and improve the ability to resist heat stress. In conclusion, the suitable level of DCAB was 228 meq·kg-1 DM in diet of heatstressed beef cattle.