In this paper, guidance laws in the direction and perpendicular to the line-of-sight is designed. The tangential component of missile acceleration is designed for zeroing the LOS rate and the other component is for controlling the closing velocity. In this method, because of using the sliding mode control, the nonlinear equation of motion is used and the acceleration command input is determined considering the target acceleration as an uncertainty. Therefore the guidance laws are robust with respect to target maneuvering and precise measuring or estimating of target acceleration is not required. In these guidance laws there are parameters for adjusting the reaching time to sliding surfaces and for producing smooth command acceleration and removing the chattering phenomenon in control input, continuous approximation method has been applied. Because of using a new sliding condition, the boundary layer is adjust only once and is independent with the designing parameter.