According to the application of multi-constellation receiver on range test, for improving the position precise of satellite navigation system，Beidou and Global Positioning System(GPS) are integrated to increase visible satellites. By analyzing the relationship between Geometric Dilution Of Precision(GDOP) and satellite position precise，a fuzzy selecting-satellites algorithm is proposed, which can make integrated satellites optimized. Simulation results indicate that the values of GDOP calculated by the new algorithm are close to the best one, both for single system and for double system; and the integrated system is superior to single system in satellites availability and positioning precise. The results can provide a reference for precision validation of Beidou system and the application of multi-constellation receiver on range test.