The invention relates to a data transmission device which comprises a data input interface unit, a data channel unit, a data output interface unit which are connected with each other orderly, a control unit, a memory unit and an ROM unit. The device is a unidirectional data transmission device which transmits data from a relatively low-security memory device to a relatively high-security memory device, and the data channel unit is arranged in the device to improve the data transmission speed of the device; in addition, the device adopts a nonvolatile memory unit to store history log of operation by the device, which has an only identification number and improves the security management performance of the device.