Abstract: Using Laplace transform this paper maps the governing equations and boundary conditions of incompressible viscous fluids into image space,thus at the same time,introducing the initial condition to the equations in the image space.Next,in image space the quasi-variational principles for incompressible viscous fluid are established by utilizing the variational integral method.Then transform these principles into the original space（i.e.,the time domain） by Laplace inverse transform.Finally an example are presented for demonstration.