Abstract: Seventy-six Chinese Holstein cows (with similar daily milk production, 60~100 days after parturition, at an average body weight of 650±10 kg, and at parities 3~5) were used in a feeding trial, where the efficiency of utilization of dietary protein was studied by means of nutrition models. It was shown that the efficiency of utilization of dietary RDP reached 67.7%, indicating that it was an important means for improving dietary protein utilization to reasonably select protein supplements and reduce dietary RDP. The IDCPs estimated by NY/T34-2004 and NRC (2001) were 2338.1 and 2505.4 g/d per cow, respectively, the big difference for which partly resulted from the assumption of the coefficient of RUP digestion at0.65 for all ingredients by NY/T34-2004. Such an estimate was not suitable for high-producing cow rations formulated with RUP highly digestible ingredients. The IDCP requirement for experimental cows was 2143 g/d per cow based upon the NRC (2001) nutritional requirement models. However, the supply of dietary IDCP was 2505.4 g/d per cow, and the efficiency of IDCP utilization was only 85.6%. An analysis of the contents of total EAA and methionine in IDCP showed that they caused a reduction of 12.3% in IDCP utilization.