Abstract: A transmission surface type ionizer was developed with a 2.5 mm stainless steel sheath core heating cable, and the ion source power supply was also improved. A continuous adjustable DC switching power supply was employed instead of the original AC power supply as the ionizer power supply, and a 0-20 kV DC power supply at the ground potential as the power of the immersion lens replaced the original 10 kV DC power supply suspended in -20 kV. The variation of the beam intensity of H^- in the front Faraday cup of the GIC4117 2×1.7 MV tandetron with the ionizer heating current was also shown.