Range resolution of synthetic aperture radar (SAR) is determined by the signal characteristic. In this paper, the method for wideband waveform generation of X-band SAR has been developed by Simulink and VHDL. The wideband waveform generation has applied the multi direct digital synthesizer (MDDS) algorithm that improved DDS algorithm. The proposed method can generate the wide bandwidth signal without burden of hardware by combining four difference short signals per clock. As a result of the development, generated signal has the bandwidth of 500 MHz at X-band and the maximum phase error is measured to 13 degree.