Propagation of ultrashort intense laser pulses in a plasma Bragg grating induced by two counterpropagating laser pulses has been investigated. Such a plasma grating exhibits an ultrawide photonic band gap, near which strong dispersion appears. It is found that the grating dispersion dominates the dispersion of background plasma by several orders of magnitude. Particle-in-cell (PIC) simulations show light speed reduction, pulse stretching, and chirped pulse compression in the plasma grating. The nonlinear coupled-mode theory agrees well with the PIC results. Because the plasma grating has a much higher damage threshold than the ordinary optical elements made of metal or dielectric, it can be a novel tool for controlling femtosecond intense laser pulses.