Text, link and usage information are the most commonly used sources in the ranking algorithm of a web search engine. In this thesis, we argue that the quality of the web pages such as the performance of the page delivery (e.g. reliability and response time) should also play an important role in ranking, especially for users with a slow Internet connection or mobile users. Based on this principle, if two pages have the same level of relevancy to a query, the one with a higher delivery quality (e.g. faster response) should be ranked higher. We define several important attributes for the Quality of Service (QoS) and explain how we rank the web pages based on these algorithms. In addition, while combining those QoS attributes, we have tested and compared different aggregation algorithms.The experiment results show that our proposed algorithms can promote the pages with a higher delivery quality to higher positions in the result list, which is beneficial to users to improve their overall experiences of using the search engine and QoS based re-ranking algorithm always gets the best performance.