The embodiment of the invention discloses a tamper-proof encryption method and a detection method and device of an encoding code stream. The encryption method comprises the following steps of: receiving encoded code stream data; generating a proof test value through verifying the encoded code stream data; combining the proof test value with a preset secret key according to a preset combination mode to generate a new combined secret key; encrypting preset watermark information through the combined secret key to generate encrypted information; and packaging the encrypted information and the encoded code stream data. In the embodiment of the invention, the bit position of the encoded code stream does not need to be modified, therefore, the code stream can be ensured not to be distorted whilethe code stream is encrypted; since the code stream per se is not changed, whereas the preset information is encrypted, the length of the encrypted information is not limited, and the quality of the code stream can not be lowered while the encryption demand is satisfied.