The invention is applicable to the field of mobile communication and provides an information synchronization data transmission method and an information synchronization data transmission system. The method comprises the following steps of receiving an information synchronization request sent by a mobile terminal through a host link, wherein the information synchronization request comprises the information of both the host link and an auxiliary link, judging whether to use the host link and the auxiliary link to transmit the information synchronization data according to the information of the host link and the auxiliary link, the link conditions and the information synchronization data needing to be transmitted, dividing the information synchronization data if judging that the host link and the auxiliary link are used to transmit the information synchronization data, and utilizing the selected host link and the auxiliary link to send the divided information synchronization data to the mobile terminal. According to the invention, the host link and the auxiliary link are adopted to transmit the information synchronization data between the mobile terminal and a server according to the to-be -transmitted information synchronization data and the connecting conditions of the links, so that the available resources are utilized to a greater extent, the data transmission efficiency is improved, and the transmission cost is effectively lowered.