Metasearch engines submit the user query to several under- lying search engines and then merge their retrieved results to generate a single list that is more e®ective to the users information needs. According to the idea behind metasearch engines, it seems that merging the results retrieved from di®erent retrieval models will improve the search coverage and precision. In this study, we have investigated the e®ect of fusion of di®erent retrieval techniques on the performance of Persian retrieval. We use an extension of Ordered Weighted Average (OWA) operator called IOWA and a weighting schema, NOWA for merging the results. Our ex- perimental results show that merging by OWA operators produces better MAP.