The invention discloses a data transmission method and system of a mobile Ad Hoc network. The data transmission method comprises the steps that nodes in the whole network are gathered according to the mutual distance between the nodes so that a plurality of cluster groups can be formed, information of a superior-peer-subordinate cluster group member relation starting from a cluster head is established in each cluster group; when a certain cluster group in the network receives a data package, the corresponding cluster head receives data, and the data are transmitted to end nodes from subordinate or peer nodes based on the corresponding cluster group member relation according to the information of the corresponding cluster member relation and the percentage of vacant package queues. According to the data transmission method and system of the mobile Ad Hoc network, due to the fact that the cluster group member relation information of the mobile Ad Hoc network is established, data forwarding and data processing are carried out according to the member relations, the number of nodes responsible for data forwarding and processing is greatly reduced, time is saved, and efficiency is improved.