By using L-1A lubricating oil detergency testing machine, the weigh and appearance of deposit of different types of base oil were investigated, and the high temperature detergency property of base oil was discussed.The results show that the high temperature detergency of API I base oil is better than that of API Ⅱbase oil. The content of medium and heavy aromatics and sulfur in API I base oil is obviously higher than that of in API II base oil, so API I base oil has good oxidation stability and less amount of deposit under high temperature.