Accidents often occur during the launching and arriving of superlarge diameter shield machines. The realtime risk monitoring technology adopted in shield launching is presented, so as to reduce the tunneling risks. The technology is as follows: The key procedures of shield launching are monitored in real time on basis of insitu monitoring, realtime work recording and expert system. The potential risks are evaluated on basis of the insitu monitoring data, the launching procedures and the construction schedule. Automatic warning is given in real time and countermeasures are proposed by the expert system. The technology has been applied in the construction of Changjiang West Road Tunnel in Shanghai and good results have been achieved.