Abstract: Aiming at the availability of BDS-3 PPP-B2b service, a systematic analysis has been conducted towards the availability ratio of PPP-B2b corrections, the average number of satellites with available corrections and the matching characteristics of PPP-B2b corrections. The results show that in China and surrounding areas, the availability of BDS-3 PPP-B2b corrections is between 71% and 95%, and reaches the maximum in Beijing. While that for the GPS system is between 68.5% and 88.6%, which is worse than the BDS-3. The satellite observation arcs lack of PPP-B2b corrections are mainly concentrated in low elevation angle periods for users in China and surrounding areas, and the availability of PPP-B2b corrections will increase with the increase of cut-off elevation angle. The average number of satellites with available PPP-B2b corrections for BDS-3, GPS and BDS-3/GPS systems in China and surrounding areas is about 8, 7 and 15 respectively, which can ensure effective real-time PPP service performance. However, on average, about 1 BDS-3 satellite and 2 GPS satellites cannot participate in the real-time PPP positioning due to the lack of PPP-B2b corrections for users in the area. For areas south of the equator, BDS-3 only or GPS-only system is basically unable to provide effective real-time PPP services with the average availability of PPP-B2b correction being less than 50%, but the BDS-3/GPS dual system can provide about 7 to 11 available satellites in some low latitude areas. Users should be noticed that there will be a temporary mismatching state between the orbit and clock offset corrections each time when the IOD Corr parameter changes due to the different updating frequency.