A kind of photonic crystal grating slow-wave circuit, namely the cross-section distributing two-dimensional photonic crystal slow-wave circuit (CD2DPhSWC), was proposed. And the way of designing CD2DPhSWC was put forward. To simply the design, the process was realized in two steps, firstly the calculation of the photonic band gap (PBG) for the TE polarization, and then the dispersion of the equivalent rectangular waveguide grating. The numerical results show that the bandwidth of the traveling wave tubes (TWTs) based on CS2DPhSWC is wider, and the operating voltage is lower, than that of the rectangular waveguide grating. Correspondingly, the cost of the TWTs is reduced.