Abstract: To design optical filter and optical switch with high quality and performance, by using the transfer matrix method theory and computational simulation method to draw the transmission spectrum band of 1-D photonic crystal, the degeneracy effect of the distance between two defects and the thickness of the defect on the transmission band spectrum of photonic crystal were studied and analyzed. The results show that the transmission band degeneracy of the photonic crystal is sensitive to the distance between two defects, the transmission band degeneracy is more obvious with the greater distance between two defects. When the distance between two defects is larger, the degenerate effect of transmission band spectrum is more obvious. When the distance increases to a certain value, complete degenerate of discrete transmission peak appears. When the defect thickness increases with integer times, the tendency of degenerate of transmission band spectrum of photonic crystal appears. When defect thickness increases with odd and even number of times, the degenerate speed of transmission spectrum is not the same. The former is shorter than the latter. No matter defect thickness increases with odd or even number times, the degeneracy of transmission band spectrum of photonic crystal reduces gradually. Degeneracy effect can provide the guidance for photonic crystal design of the new optical filter, optical switch and modulation mechanism.