The coupled mode theory of parallel photonic crystal resonators is analyzed, based on which, a side-coupled waveguide to achieve the efficient coupling between photonic crystal devices and the light source is proposed. The theory analysis indicates that the coupling efficiency is sensitive to the total number, the interval and the quality factors of the resonators. By the optimization of the coupling efficiency and the coupling region, five parallel resonators are selected to construct the coupling part of the single channel side-coupled waveguide. Single channel propagation of the side coupled waveguide is realized through changing the interval of the resonators. The single channel side-coupled waveguide achieves the coupling efficiency of 94.49% at the wavelength of 1.55 μm.