In recent years cellular automata (CA) have been establishing increasing interests in the study of modeling and simulating non-linear phenomena occurring in biology, chemistry, ecology, economy, geology, mechanical engineering, medicine, physics, sociology, public traffic, etc. Cellular automata are considered to be a nice model of complex systems in which an infinite one-dimensional array of finite state machines (cells) updates itself in synchronous manner according to a uniform local rule. The firing squad synchronization problem on cellular automata has been studied extensively for more than forty years, and a rich variety of synchronization algorithms have been proposed. In the present paper, we propose a completely new optimum-time synchronization algorithm for laarge-scale- of two-dimensional cellular automata. The algorithm can synchronize any two-dimensional array of size m? n in optimum m + n + max(m, n) - 3 steps. A simulation result is also given.