Abstract: Based on statistical analysis, an interesting fact is revealed that in winters prior to El Nino (La Nina) events occurred through 1951—1987, East Asia trough is weaker (stronger) than in the normal years. The composited field of 500 hPa height anomalies for 10 winters prior to El Nino events also shows significant positive anomalies over East Asia. The results of power spectrum and cross spectrum analyses indicate that the relationships between the trough intensity and the SST of the eastern equatorial Pacific are obvious. Both the trough and the SST in seasons have the most significant 3—4 year period oscillation, respectively, and the oscillation of the trough precedes that of the SST by 4—8 months