A novel ridged double staggered grating (RDSG) slow wave structure (SWS) is put forward to develop the wide-band and high-power terahertz radiation source for meeting the demand of thriving field of terahertz. The high frequency structure of backward wave oscillator (BWO) is designed and optimized, meanwhile high frequency characteristics of RDSG and double staggered grating (DSG) are simulated and compared, indicating that RDSG has a higher ‘cold’ bandwidth and more prominent interaction impedance when their phase velocity are adjusted to basically the same. PIC simulation results show that, ridged double staggered grating backward wave oscillator has a tunable bandwidth more than 175 GHz, and it can generate more than 1.1 W output power which is 34%～42% higher than BWO implemented with conventional DSG in the frequency range around 1 THz.