Duroc native to the eastern United States of New Jersey and New York and other places, is one of the world famous pig breeds, with strong physique, strong adaptability, fast growth, feed utilization rate, better meat quality properties, mainly is the father of commercial pig production in the product line. Now the introduction of the new American Duroc (the American Duroc) after years of breeding of foreign breeding experts, and has had on the genetic, pig production performance changes, huge 1. Compared with foreign reports, there are some differences in litter size among imported pigs in China, which may be related to many factors, such as climate, feed, feeding, management and so on. [2]. Sow is the basis for the development of pig industry. How to make good use of sows and improve the reproductive performance of sows is the key to healthy and effective development of pig industry, and is also the focus of current genetic breeding research. The analysis of influence on the reproductive performance of the year, season, parity, environment and other aspects of American Duroc.