In this paper，a structure of T-shaped photonic crystal filter based on ring resonators is presented.We have investigated the transmission properties of the filter by using finite-difference time-domain method,and analyze the effects of photonic crystal structural parameters to its transmission properties.The results of analysis show that this structure has properties of tunable switch wavelength,high normalized transmission,and a large bandwidth.It has application value in the designs of photonic crystal integration and optical communication devices and so on.