Abstract: In order to construct compact free-electron laser facility, and to study on free-electron laser technology, it is necessary to develop a microwave RF gun as high-quality electron beam source. Therefore, an independently-tunable-cell(ITC) thermionic-cathode RF gun is manufactured in CAEP. Based on the preliminary power test results obtained before, more experiments are launched and experimental results are examined in depth by improving experimental environment and optimizing experimental parameters. The experimental results show that, a beam intensity over 500 mA can be measured at exit of the RF gun, and the back electron bombardment can be changed with adjustment of phase and amplitude of the electric field in the first cavity. At present, the thermionic-cathode RF gun has had applications in compact free-electron laser facility already.