Xu, Y. Chen, Y. Ding, K.Z. Gu, K. Huang, X.Y. Li, J. Pei, K. Song, Y. JACoW Publishing Geneva, Switzerland 978-3-95450-205-9 10.18429/JACoW-Cyclotrons2019-MOP003 English 27-30 MOP003 septum proton simulation cyclotron extraction Contribution to a conference proceedings 2020 2020-06 https://doi.org/10.18429/JACoW-Cyclotrons2019-MOP003 http://jacow.org/cyclotrons2019/papers/mop003.pdf In recent years, the study of proton therapy equipment has received increasing attention in China. Hefei CAS Ion Medical and Technical Devices Co., Ltd. (HFCIM) is developing a proton medical device based on the super-conducting proton cyclotron. The electrostatic deflector (ESD) is the key extraction component of the SC200 superconducting cyclotron, which uses a high-intensity electric field to bend the beam from the track. The fierce interaction between the proton beam and the deflector septum, causes a great loss of beam and unwanted excess heat accumulation and radiation. In order to minimize the risk of damage caused by the proton beam loss, the fluid solid-thermal coupling analysis of the deflector was per-formed by applying computational fluid dynamics (CFD) on ANSYS. The maximum temperatures of the septum in various cases of the cooling water speed, the septum thickness and material have been investigated respective-ly. The result based on analysis provide a valuable refer-ence for the further optimization on the material selection and structural design for ESD.