To improve the positioning accuracy and reliability of Beidou ,an analysis of the Beidou satellite navigation system has been performed; combination of technical experience of the foreign global satellite navigation system and the current release of technical information, we have designed Beidou satellite navigation system constellation, by satellite visibility analysis and a variety of DOP's numerical comparison of the different design options, we can prove the Beidou second-generation constellation program can meet the needs of the global satellite location, especially in China and its surrounding areas, the designed Beidou second-generation satellite navigation system have more precise positioning compared to other global navigaiton system. KeywordsBeidou satellite navigation system; satellite constellation design; the DOP value; simulation