The influences of the thickness of defect layer on the resonant wavelength and its quality factor in one-dimensional photonic crystal cavity were studied with optical transmission matrix. Numerical simulations show that there exist different mode types and a maximal quality factor for each mode type. The maximum is found at the wavelength λm where there is a maximal reflection from the photonic crystal, corresponding to the condition for resonance Bragg reflection. The quality factor and thickness of the defect layer corresponding to λm are in linear relations with the mode order number. The quality factor increases exponentially with the number of the structural periods, and the increment number is only a function of the operating wavelength, and has no relation to mode types and periods of structure. For all mode types, the increament number reaches a maximum at the wavelength λm.