The design, simulation and measurement of the microwave cavity for the cold atom clock are presented. Single-ended loop coupling is used to stimulate the microwave field. Based on the result of simulation, the loop coupled from the side surface of the cylindrical cavity will induce a more symmetric microwave field than that coupled from the end face. The mode selection is realized by finely tuning the coupling loop. This method is not only simple, but it can also effectively reduce the volume of microwave cavity. Finally, the microwave cavity developed is tested and the results indicate that the performance of the microwave cavity meets the requirements of stable integrating sphere atom clock with small volume. Moreover, no reflective coating, which will affect the microwave field pattern, is needed for cooling atoms. This is beneficial to enhance the clock signal, and finally will improve the signal to noise ratio and the contrast.