when workover operations were performed in Bohai S oilfield，a high permeability and porosity heavy reservoir，using source water as workover fluid，there was the problem of large amounts of fluid leak into formation and poor productivity recovery effect. In order to decrease the formation damage of extraneous operating fluid，a workover fluid which could protect formation was developed. Boundery film washing agent，viscosity reducer，anticrustator and clean up additive used to prepare prepad fluid was optimized by laboratory experiment，and the viscosity increasing property of temporary plugging fluid（TPF）and the plugging performance of the TPF for core and permeability recovery of the core after gel breaking were evaluated. The experiment results showed that the displacement efficiency and viscosity reduction rate of prepad fluid，composed of 15% boundery film washing agent GXXJ + 1.5% viscosity reducer JN-01，0.5% anticrustator ZG-02 and 1% clean up additive ZP-01，was greater than 90% ，respectively，Besides，it could inhibit calcium and magnesium scaling and reduce flowback pressure by 50% . Under the circumstances of 3.5—4 MPa and 60℃，the temporary plugging fluid，composed of 3% oil soluble temporary plugging agent BH-ZD+0.7% viscosity Increaser BH-VIS +3% gel breaker JPC，showed well plugging capacity，moreover，after gel breaking，the permeability recovery rate of core was more than 80% . The workover fluid，composed of prepad fluid and temporary plugging fluid，could prevent organic precipitation and other formation damage. The workover fluid had been applied in S oilfield，after workover，the leakage of operating fluid was low and productivity recover was well.