Abstract: The objective of seismic rock-physics is to study the relationship between lithology,fluid and elastic parameters of rocks. This technology has the advantage to establish the basic criteria for reservoir and hydrocarbon prediction upon seismic data. In the oilfield Bohai A, the inversion of post-stack impedance is not enough to identify the reservoir fluid properties and the changes in fluid types. Water saturation and porosity have effect on the response of well data and seismic amplitude. In order to know better about the effect, we use fluid replacing and forward simulation technology to guide the reservoir research and hydrocarbon testing. The technology can be promoted to the oilfields with similar reservoirs.