Precise point positioning (PPP) ambiguity resolution (AR) has been demonstrated as an effective tool to improve the positioning accuracy and shorten the convergence time. Under the multi- system and multi-frequency environment, it is anticipated to achieve the first ambiguity-fixed solution within few minutes. The development of LEO satellites, with fast geometric change and high signal strength, provides the great opportunity for improving the PPP ambiguity resolution. In this contribution, we investigated multi-constellation GNSS (multi-GNSS) and multi-frequency PPP AR based on triple-frequency observations from different GNSS (GPS, Galileo, and BDS), and also evaluated the performance of the PPP rapid ambiguity resolution with LEO constellation augmented GNSS. For PPP ambiguity, the multi-frequency uncalibrated phase delay (UPD) products of GNSS and LEO satellites were estimated firstly and the quality of the UPD products in terms of temporal characteristic, usage rate as well as the residuals was also analyzed. Numerous results show that the performance in terms of positioning accuracy and convergence time can be obviously improved by multi-GNSS and multi-frequency PPP ambiguity resolution. An averaged time to first fix (TTFF) of 9.21 min with 7° cut-off elevation angle can be achieved for four-system PPP AR and the hourly positioning accuracy is improved by about 40% with multi-GNSS triple-frequency PPP AR. With the augmentation of 288 LEO satellite, the TTFF of GNSS PPP AR can be shortened to about 40s. The positioning accuracy of multi-GNSS fixed solutions was also improved by about 70% and 90% with the inclusion of 60 and 288 LEO satellites, respectively. Moreover, LEO-only PPP AR is first explored with the TTFF of 1.6 min, which is even better than the performance of GNSS PPP AR because of the rapid change of spatial geometry.