According to the time domain coupled mode theory, the working conditions of the photonic crystal stop-band filter with a side coupling structure of the waveguide and the approximate rectangular ring cavity resonator are analyzed. The function relationships of normalized stop-band loss L, cavity detuning factor|ω-ω0|τ0, cavity normalized loss Lc, normalized reflection R and normalized transmission T are obtained, and the stop-band loss mechanism of PCSBF is explored. The filtering performance of PCSBF within the wavelength range of 1450--1750 nm is studied by using the finite difference time domain method, which shows that the stop-bands of the output normalized power spectrum can be adjusted by changing the size of 3×n(3≤n≤9)approximate rectangular ring cavities or by changing the radius of inner rods in this PCSBF structure. 34 wide stop-bands whose average width is 5817 nm are collected from the PCSBF power spectrum, and the average value of these stop-bands signal strength decay is not less than 8035 dB. The results show that the stop-band of the structure has the characteristics of wide tenability, high normalized loss and so on. According to the actual demand, changing the PCSBF structure design to adjust the power output spectrum can effectively filter the unwanted wavelength signal, thus ensuring the stability of optical fiber communication system and integrated optical path. Therefore, this miniature stop-band component has potential application value in the optical integration, the optical communication and other fields.