This paper introduces the principles of pulse shaping by method of spatialtemporal transform. It is pointed out that a slit of light fluence modulator would cause dynamical discordance of spatial intensity distribution. The solution is presented and certified by two dimension FFT stimulation mathematically. Finally the dependence of system transmission factor on focued beam spot size and width of the slit is caculated.Experimentally a complex pulse is got, which is typical one for ICF experiment to demonstrate the shaping ability of the system.