A theoretical model of Michelson interferometer in a two-dimensional rod-type photonic crystal (PhC), is proposed and numerically demonstrated. The MI includes one splitter and two mirrors. Lights propagate between them independence on self-collimation effect. The two interferometer branches have different path lengths. By using the finite-difference time-domain method, the calculation results show that the transmission spectra at the output ports are in the shape of sinusoidal curves and have a uniform peak spacing in the frequency range from 0.192c/a to 0.200c/a. When the path length of the longer branch is increased and the shorter one is fixed, the peaks shift to the lower frequencies and the peak spacing decreases nonlinearly. For the operating wavelength around 1550 nm, the whole structure is about tens of microns .So it may be applied in future photonic integrated circuits.