Chen, W. Fan, K. Liang, Z.K. Liu, K.F. Liu, X. Qin, B. JACoW Geneva, Switzerland 978-3-95450-167-0 10.18429/JACoW-Cyclotrons2016-MODM01 English 33-35 MODM01 proton cyclotron extraction magnet-design acceleration Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-Cyclotrons2016-MODM01 http://jacow.org/cyclotrons2016/papers/modm01.pdf Superconducting cyclotron is an optimum choice to deliver high quality continuous wave (CW) proton beams for proton therapy with its compactness and power saving. Field isochronism and tune optimization are the two crucial factors of cyclotrons during the magnet design. This paper is concentrated on the superconducting magnet design, mainly including the spiral magnet, isochronous field and the tune optimization. The main parameters and some features of the machine will be presented.