The invention provides a method and system for safely switching between product mode and development mode of a terminal, aiming at addressing the problem in the prior art that the terminal in a testing development version may be accidentally circulated into the market and cause hidden safety risk. According to the invention, different Certificate Authorities (CAs) are configured for the terminal at different stages; by storing the public-private key pairs of the certificates issued by different CAs in different secure storage media, only if the secure storage medium corresponding to the current CA state of the terminal is verified to be valid, the flags of the terminal can be successfully rewritten; a safe switching between different CA states of the terminal is realized. It is ensured that the terminal in the testing development stage cannot be used normally even if it is erroneously circulated into the market as a format product, and the interests of users and operators can be guaranteed, thereby improving the safety of the terminal device and achieving safe and fast switching.