|| Taiwan is a member of the three organizations in the Pacific Ocean (WCPFC, IATTC) which imposes the responsibility of enhancing researches on Taiwanese tuna fisheries. This project is to review and screen historical operational level catch data of tropical tunas of Taiwanese large-scale longline fishery in the WCPO, based on outlier detect methods, in the stratum of target fishing periods and target fishing grounds. The result will also be compared with observer data. CPUE standardization will then be performed on the final dataset and the effect of outlier-screening will also be reviewed according to the improvement of the standardization. The results suggested that although the coverage rate of small-scale longline data was still low, the consistency was very high for those data comparable in both-sides. As to the large-scale longline data, both sides hold data from different size of vessels and therefore were combined for the standardization purposes. The standardization process performed better with Taiwanese data included. The standardized series showed a declining trend until 1997 for both species and remained at a low level thereafter. On the other hand, the effects of screening Taiwan large-scale longline data are obvious in some specific region (reg5 and reg6) and some years. However, for both the pre-screened and post-screened data, the consequent standardized CPUE series all showed declining trends in recent years.