A method for producing a high strength coated steel sheet having a yield strength YS of at least 800 MPa, a tensile strength TS of >1180 MPa, a total elongation >14% and a hole expansion ratio HER>30%. The steel contains in weight %: 0.13%≦C≦0.22%, 1.2%≦Si≦1.8%, 1.8%≦Mn≦2.2%, 0.10%≦Mo≦0.20%, Nb≦0.05%, Al≦0.5%, the remainder being Fe and unavoidable impurities. The sheet is annealed at a temperature TA higher than Ac3 but less than 1000° C. for more than 30 s, then quenched by cooling temperature QT between 325° C. and 375° C., at a cooling speed sufficient to obtain a structure consisting of austenite and at least 60% of martensite, the austenite content being such that the fmal structure can contain between 3% and 15% of residual austenite and between 85 and 97% of the sum of martensite and bainite, without ferrite, then heated to a partitioning temperature PT between 430° C. and 480° C. and maintained at this temperature for a partitioning time Pt between 10 s and 90 s, then hot dip coated cooled to the room temperature. Coated sheet obtained.