The impulsive spin-up flow in a shallow rectangular container is analyzed numerically by quasi 3-D unsteady laminar flow. In the non-inertia coordinates, the flow is generated by the virtual forces as Coriolis force, etc.. After the boundary layers grow up near sidewalls, primary vortexes separate from the sidewalls. As the Reynolds number increases, the subsidiary vortexes take place in the boundary layer. The rigid body rotation is started from the inner region and propagated to the outer region, finally all the fluid reaches the rigid body rotation. According to the Reynolds number and the aspect ratio, the development of vortex pattern is symmetric or asymmetric.