This paper presents results on the impact of Laser CO2 process variables on the weldability, phase transformations and exhibited tensile properties in a TRIP800 Steel. The microstructures of this steel consist of ferrite, bainite, martensite, and substantial amount of retained austenite, which is obtained by controlled cooling from the intercritical anneling temperature to the isothermal bainitic holding temperature. These steel has been increasingly used in the last 10 years in the automotive industries and for these materials to be used effectively, the influence of material and the Laser CO2 process condition must be clearly understood. Hence, in this work the effect of the welding process on the resultant microstructures and on the exhibited mechanical properties was investigated. Color tint etching applied in welded for AHSS help us to know the phase transformation, the colors of each phase viewed under the microscopy. The weld was etching with Klemm´s 1 solution, in this work; it was found that the bainite is clearly identify by blue color, the martensite brown, yellow ferrite and the retained austenite white. Additional X ray Diffraction (XRD) is employed in characterization to estimate the quantity of retained austenite.