Disclosed are a method and a system for protecting data. The method for protecting data provided by an embodiment of the present invention comprises: in an initialization process of a device where data are located, acquiring an environmental factor according to environment information of the device in a secure environment; and encrypting sensitive data in the device by utilizing the environmental factor in the secure environment, and after determining that the encryption succeeds, destroying the environmental factor. Each time the device is started, an environmental factor is acquired according to the environment information of the device in the current environment, and then the encrypted sensitive data in the device is decrypted by utilizing the environmental factor in the current environment; when the decryption succeeds, access to the data in the device is allowed, and when the decryption fails, access to the data in the device is denied. The hardware cost required by the solution is low, and the risk of data leakage can be greatly reduced.