The invention relates to a light-weight time synchronization method oriented to a large-scale ad hoc network, and aims to solve the problems that the overhead in an existing time synchronization method is large and the method cannot be actually applied to a wireless sensor network. The method comprises network time resource partition based on a time division multiple access (TDMA) thought, construction of a node hierarchical structure, node time synchronization, and adaptive adjustment of a synchronization period according to sub-node synchronization accuracy. As proved by testing and simulation, the method has the advantages that relatively high network synchronization accuracy can be obtained; the synchronization period can be adjusted adaptively according to the sub-node synchronization accuracy on the premise of ensuring normal interaction of data among nodes; and the network synchronization overhead is reduced greatly. The light-weight time synchronization method oriented to the large-scale ad hoc network can be well applied to the large-scale ad hoc network, and the network synchronization power consumption is lowered greatly.