Three QZSS satellites are launched in 2017,which implies that a four satellites regional system is to be established in 2018.There is no doubt that QZSS will play a more important role in the future global GNSS constellations.So it is quite necessary to investigate the importance of current QZSS constellation in positioning.In this paper,the number of visible satellite and PDOP(Position Dilution of Precision)value improvement by combining QZSS with the existing GPS and BeiDou system is analyzed among Asia-Pacific areas.