The invention provides a twin-core watt-hour meter data exchange validity determining method. A twin-core watt-hour meter comprises a management part and a legal measurement part. The method comprises the following steps: the legal measurement part generates a random number R after receiving a communication request sent by a client or a principal computer via the management part, and sends the random number R to the client or the principal computer via the management part; the legal measurement part acquires target data T and calibration data C1 sent by the client or the principal computer, the legal measurement part uses a pre-stored key A to encrypt the random number R according to a pre-stored encryption algorithm to get a temporary key B, and the legal measurement part uses the temporary key B to perform computation on the target data T according to the pre-stored encryption algorithm to get calibration data C2; the legal measurement part judges whether the generated calibration data C2 and the received calibration data C1 are consistent through comparison, the target data is valid if the calibration data C2 and the calibration data C1 are consistent, and the target data is invalid if the calibration data C2 and the calibration data C1 are not consistent.