Abstract: The Dragon-Ⅱ injector is a strong current pulse electron beam source, it is an inductive adder with thermal cathode and provides three pulse beams with adjustable pulse interval for Dragon-Ⅱ LIA. The way with cross validation and mutual promotion of PIC simulations and experiments is adopted during the injector beam tuning. First, the magnetic field loading range of the leading solenoid is determined approximately by the beam spot measurements. Second, the magnetic field configuration of every solenoid installed in the anode beam line is simulated by PIC step by step, and then confirmed by the beam spot measurements. By this means, three kinds of magnetic field configurations which can keep the pulse flat-topped completely are obtained in order to meet the different requirements of the downstream beam transportation. Finally, the factors affecting the effects of beam tuning are discussed and the key to the injector performance improvement is considered to be further improving the emission uniformity of the large area thermal cathode.