Data transmission method and system

The invention provides a data transmission method and system, and relates to the field of information security. The method comprises the following steps: under the condition that a detection terminal detects that a third-party device intercepts flow between a first device and a second device, a mode switching instruction is sent to the first device and the second device respectively, so that the first device and the second device are switched from a data security mode to a data anti-theft mode; after the first device is switched to the data anti-theft mode, the first device encrypts original data according to a preset anti-theft encryption process to obtain anti-theft encrypted data sent to the second device, so that a third-party device cannot crack the anti-theft encrypted data after intercepting the anti-theft encrypted data; and after the second equipment is switched to the data anti-theft mode, the received anti-theft encrypted data is decrypted according to the preset anti-theft decryption process match