Due to too many coupling parameters involve in laser arc hybrid welding, in order to obtain a good hybrid welding, a lot of parameter optimization work is usually required to obtain a relatively stable process parameter window. To shorten the experimental period and find out the inherent mechanism of unstable state, in this work, the experimental design method was used to study the surface forming and process stability of the distance laser-arc, welding voltage, laser power, and laser+pulse melting gas metal arc hybrid welding (GMAW). Though high speed photography and electrical signal system, the reasons for the difference of forming law were explained. The results show that higher voltage and smaller distance laser-arc will lead to instability of welding process. The reason for this phenomenon is that the force mode and size of droplet change, and finally the droplet drop point deviates from the moving direction of the welding gun.