To construct a 5 MW neutral beam heating beamline for HL-2M device, the development of the discharge chamber of the hot cathode arc discharge ion source for neutral beam heating was carried out. The neutral beamline contains four sets of 80 kV/45 A/5 s ion sources, and the discharge chamber design index is 850 A/5 s. Firstly, the electromagnetic studio in CST software was used to simulate the cusp magnetic field of the discharge chamber with specific geometric structure, and the cusp magnetic field distribution was obtained, which verified the rationality of cusp magnetic field layout. To solve the problems in the process of the discharge chamber and the localized arcing in the experiment, the structure of the discharge chamber was improved. The side wall of the discharge chamber changed from 40 rows of cusp magnets to 7 rings of cusp magnets, the cathode structure changed from the filament plate structure to the ceramic kovar structure, and a ceramic shield was added between the discharge chamber and the accelerator. Normal arc discharge was obtained in both the cathode plate discharge chamber and the cathode ceramic kovar discharge chamber. The final shaped discharge chamber adopted 7-ring cusp magnets and ceramic kovar cathode structure. The arc discharge index of the 5 MW neutral beamline ion source was achieved in the final shaped discharge chamber. The arc discharge time was close to 5 s, and the maximum arc discharge current reached 1 000 A.