A bridged-T type all-pass network is introduced in this paper with its calculation results and frequency responses. With the utilization of this all-pass network

a new type of tuning-free RF acceleration cavity is obtained for synchrotron. The merits of better performance of such a tuning-free RF cavity than the conventional tuning RF cavity make it very attractive in synchrotron application. The possibility of using such a tuning-free RF cavity in HIRFL-CSR (Cooler Storage Ring) project at Lanzhou is also discussed. By applying multiple-frequency flat-topping acceleration technique

the capture efficiency of the radioactive ion beam of large emittance at CSR will be enhanced.