The reservoir of S4z in PFW oilfield, structure, microstructure, depth and fault affected fluid propertiesand distribution law. The high and low density and viscosity of crude oil are corresponding with low andhigh total salinity of formation water in plane. There is high heterogeneous of fluid properties in verticaland four types of fluid which are gas, light oil, heavy oil and water, it has general uniform interfacebetween two contrast fluid . At the same time, dynamic variation of fluid properties was gotten duringwater flooding in Saturated oil reservoir which included gas cap through researching. The law ofdistribution and variation can Provide scientific basis for formulating and adjusting development plan andfor numerical simulation. The high water and low density and viscosity of crude oil are corresponding with low and high total salinity of formation water in plane. There is high heterogeneous of fluid properties in verticaland four types of fluid which are gas, light oil, heavy oil and water, it has general uniform interface between two contrast fluids through researching. The law ofdistribution and variation can Provide Scientific basis for formulating and adjusting development plan and for numerical simulation.