In this paper, we study the global clock synchronization and ranging problem for wireless sensor networks in the presence of unknown exponential delays using the two-way message exchange mechanism. Based on the Alternating Direction Method of Multipliers (ADMM), we propose a fully-distributed synchronization and ranging algorithm which has low communication overhead and computation cost. Simulation results show that the proposed algorithm achieves better accuracy than consensus algorithm, and can always converge to the centralized optimal solution.