Abstract: For big data has been pervasively applied in many industries as crucial information supports and confronted with lots of security risks in the procedure of collection, storage, transmission and application, this paper analyzes the security threats in big data's life cycle, summarizes the security critical technologies and new developments according to big data system platforms and big data applications, including user access control, data isolation, data integration, privacy protection, security audit, precaution advanced persistent threat etc., to meet the new security challenges and requests proposed by the rapid developments of cloud computing, Internet of Things, mobile internet, etc. It also prospects the security tendency for big data.