A new proton therapy facility with 230 MeV SC cyclotron is being built by China Institute of Atomic Energy(CIAE). An internal cold-cathode ion source is designed and tested, which will be mounted in the SC cyclotron central region. It consists of a chimney, an upper and a lower cathode fixed by the chimney. The design considerations and some testing works are presented. The magnetic field in the central region is about 2.35 T, and there is a rf bridge passing though the central region, so there is a little space for the ion source. So, the ion source is small, the chimney size is only Φ1.5 mm × 50 mm, the extraction slit is 2 × 0.5 mm, and the tilt angle is 30 degrees. The experiments have been done on the test stand, and the beam properties for different settings of the ion source will be presented in the paper.