Abstract: Self-shielded flux cored wire is a kind of welding material suitable for field project, which is widely used in welding and repair of field project such as ships, drilling platforms, oil pipelines and containers. Single-layer single-bead welding was carried out on the surface of Q235 steel by self-shielded flux cored wire, and quadratic regression mathematical model between arc voltage, wire feeding speed, welding speed and melting width, reinforcement, melting height was established by quadratic regression universal rotating combination design method. The relationship between process parameters and deposited geometries is analyzed, the results show that the model can predict the influence of process parameter variation on the geometry of the deposited layer in the stable process interval. The wire feeding speed is the main factor affecting the melting width and reinforcement at low voltage, while the welding speed is the main factor affecting the melting width and reinforcement at high voltage.