A large amount of oily sludge will be produced in the process of petroleum exploitation. In order to solve the problems of oil waste and environmental pollution in this process，based on the analysis of the basic composition of oily sludge，the hot water/chemical cleaning method was adopted to degrease the oil sludge in Tahe oilfield. The effects of detergent concentration，cleaning temperature，stirring rate，stirring time and liquid-solid ratio on residual oil rate were investigated using surfactant QT9 and alkali as cleaning agentsby single factor and orthogonal experiments. The experimental results showed that when the concentration of QT9 was 0.6%，the concentration of mixed alkali was 3%，the cleaning temperature was 25℃，the stirring time was 30 min，the stirring rate was 210 r/min and the liquid-solid ratio was 3∶1，the oil content of sludge could be reduced from 14.3% to 1.3% by twice cleaning. The orthogonal experiment results showed that the influence factors to the residual oil rate were arranged as follows：temperature > dosage of main agent > dosage of auxiliary agent > liquid-solid ratio. Thermogravimetric analysis showed that the crude oil composition in the sludge decreased significantly after cleaning