The influencing factors  for the light-off characteristics of diesel oxidation catalyst (DOC) were studied on a medium-duty diesel engine according to the current China Ⅵ emission regulation. According to the different coating methods and noble metal proportion of DOC catalyst, three different schemes were designed which were labeled as Plan A Plan B and Plan C respectively. The total noble metal content of three schemes was the same. The proportions of Pt and Pd were different in front and back zone for Plan A and Plan B, and the proportion of Pt increased in Plan C. Besides, the aging tests were carried out in two stages respectively, and the light-off characteristics were studied under different working conditions. The results show that the DOC catalysts of three coating methods from Plan A, Plan B and Plan C can meet the lightoff performance requirements. Plan B and Plan C have higher HC conversion efficiency and better lightoff performance, which have certain advantages for guaranteeing lightoff and controlling HC leakage.