Abstract: Systematic study was conducted on fundamental characteristics and pretreatment process of super viscous oil emulsion wastewater.It was shown that the technical keys points are:①adopting proper process parameters for oil separation to effectively separate the crude oil and residuals in the wastewater,and ②adopting suitable flocculation process to guarantee the effluent water quality from air floatation and minimize mineral oil,residual and COD from pretreatment effluent.The process of low-loading oil-separation precipitation and high-loading dissolved air flocculation (DAF) was thus proposed.With longer hydraulic resident time in Precipitation Tank,the recovery rate of crude oil in the wastewater can be 80% and the removal rates of mineral oil,residual and COD of secondary air flotation complex process can be 99%,98% and 86% respectively.The process and parameters can be applied for design of 800 t/d wastewater plant and the operation can be stably and reliably.