This paper points out that traditional early warning procedures are oversimple and differences in average lead time of leading indicators are neglected. Aiming at those problems, a multi-time-scale early warning system is designed, in which the early warning procedure is divided into three levels, long-term, mid-term and short-term level, so that to meet different early warning demands in different situations. Accordingly, the leading indicators are divided into three levels too. The multi-scale early warning system is applied to the Philippine Currency crisis of 1997. Conclusions show that the system has better early warning capability.