On the basis of the full investigation of oversea riserless intervention operation equipment， the history， the technology benefit and the operational capability of riserless intervention technology are introduced. Summary and comparative analysis are carried out for the existing riserless intervention techniques and equipment. The global riserless intervention service providers are summarized. Finally， the development trends of riserless intervention operations and equipment are concluded， and an outlook is presented for carrying out the riserless intervention study in China.