In our country's global navigation system, namely BDS-3, 19 satellites (18 MEO satellites and 1 GEO satellite) have been launched in the period from November 2017 to November 2018. The basic system of BDS-3 has been set up and is going to provide essential navigation service for the countries and districts in "the Belt and Road" starting from the end of 2018. The signal features of B1I/B1C, system visibility and performance of the navigation system are thoroughly studied based on self-designed "GaoJing-1" multi-mode multi-frequency receiver. Through analyzing the measurement results, the receiver can observe the 5 experimental satellites and all the satellites of BDS-3 except GEO-1(PRN59) and MEO-8(PRN48). Although the BDS-3 system is still in the debugging phase, the health flag is 1 for signal B1I, and 1 or 2 for B1C, which means that the receiver should not use the signals from B1I and B1C for positioning. However, we still try to get the positioning. The experiment results indicate that, utilizing the almanac with intermediate precision broadcast by B1C, when the cut-off angle is 10 degrees and 20 degrees, the minimum number of visible satellites in 24 hours at Beijing for BDS-3 is 6 and 5 respectively, and the success rate of positioning is 100%. And the BDS-3 provides a better positioning accuracy than BDS-2. When using the signal B1I and B1C of BDS-3, the standard deviation of positioning error is 21% and 28% lower than that of BDS-2 respectively. When using the combined positioning of BDS-2 and BDS-3, the positioning error is 45% than that of BDS-2, and 31% lower than that of BDS-3.