RSS is the XML-based format for syndication of Web contents and users aggregate RSS feeds with RSS feed aggregators. As the usage of RSS service has been diffused, it is crucial to have a good aggregation policy that enables users to efficiently aggregate postings that are generated. Aggregation policies may determine not only the number of aggregations for each RSS feed, but also schedule when aggregations take place. In this paper, we first propose the algorithms of minimum missing aggregation policy which reduces the number of missing postings during aggregations. Second, we compare and analyze the experimental results of ours with the existing minimum delay aggregation policy. Our analysis shows that the minimum missing aggregation policy can reduce approximately 29% of the posts the existing minimum delay aggregation policy would miss.