Abstract: Heavy ion research facility at Lanzhoucooler storage ring (HIRFL-CSR) is being constructed. It consists of a main ring (CSRm) and an experimental ring (CSRe). The aim of the main ring is to accelerate the heavy ion to high energy. For synchronization between bending magnet field and RF frequency during acceleration process, two beam feedback loops for the frequency control are needed. One is the phase loop and the other is the radial position loop. The effects of these loops on the beam dynamics in the synchrotron are analysed on the basis of Laplace transformation and some numerical calculations.