The time-dependence of the forecast skills of IAP ENSO Prediction System was analyzed based on the hindcasts for the period from November 1981 to December 1997. The results indicated that the forecast system showed the higher skills for the ENSOs in 1980s than that in 1990s. The correlation coefficients in Nino 3 region were near 0.8 at a lead time of about one and half years in 1980s, while it reduced to about 0.4 after a half year in advance in 1990s. The seasonal-dependence was also shown that the forecasts initiated from spring to autumn were more skillful with the correlation skills above 0.5 maintaining more than 15 months, where those initiated from July to September showed the skills above 0.6 within 16 months in advance. The skills of the prediction initiated from later autumn to winter were lower, which decreased rapidly to below 0.5 after 5 months. The near real time prediction for the rn1999's La Nia event was successful in term that this event would persist to 2000, but its re-strengthening was not predicted properly. The prediction for the future shows that the cold episode conditions will return to near-normal or week-warm conditions in the later summer or autumn of this year.%利用IAP ENSO预测系统对1981年11月至1997年12月系统性回报实验的结果，分析了预报技巧的时间依赖性。结果表明：该预测系统对80年代的ENSO具有较强的预报能力，在Nino 3区接近0.8的预报相关技巧（预报与观测的相关系数）可达1年半左右，而对90年代的ENSO现象，预报技巧则较低，超前半年以上的预报仅在0.4左右；预报技巧具有季节依赖性，从春季到秋初开始的预报较好，高于0.5的技巧均可维持15个月以上，其中从7月到9月开始的预报，其高于0.6的相关技巧可达16个月；而从秋末和冬季开始的预报，其技巧衰减较快，预报5个月后降到了0.5以下。对1999年La Nia事件的实时预测总体上是成功的，即此次La NNia事件将维持到2000年；但未能预测出其在1999年春季以后再次加强的过程。对其未来变化趋势的预测显示，此次La Nia事件有可能于今年夏秋季结束。
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