The dynamic properties of forward and backward waves in the fiber grating are studied. The results show that forward and backward waves amplitudes develope sinusoidally along the grating, the number of their amplitude maximums is equate to the corresponding rank of wavelength,thei rmaximums are dependent of the wavelength rank and independent of their position in the grating, and theirmaximums distribute periodically along the grating; the minimum of backward wave amp litude is zero.