正常情况：联程机票转机不需要过境签，但非联程就要。
自2016年1月4日起，经南非约翰内斯堡坦博国际机场、开普敦国际机场、德班沙卡王国际机场和约翰内斯堡拉塞利亚国际机场过境前往南非六个邻国（津巴布韦、纳米比亚、莱索托、博茨瓦纳、斯威士兰及莫桑比克）的旅客，无须办理过境签证。
但现在是否还执行些规定，建议与该国使馆确认一下为好。

聯程機票肯定不需要南非簽證，非聯程機票詢問承運航司客服。

With effect from 18 December 2015 travellers, with the exception of deportees, who transit through O R Tambo International Airport; Cape Town International Airport; King Shaka International Airport and Lanseria International Airport do not require transit visas as contemplated in section 10B(4)(a) of the Immigration Act, 2002 (Act No 13 of 2002). However, transiting passengers will be subjected to biometric capturing. Deportees transiting at any port of entry are required to be in possession of a transit visa at all times and must be escorted.
我终于从南非内务部网站查到了这句话