High-precision ionospheric model is of great significance for improving the positioning accuracy of navigation satellite system. With the rapid development of low earth orbit satellites, the establishment of a high-precision ionospheric model has provided new opportunities. Based on the simulation data, this paper obtains LEO (low earth orbit) and GNSS (global navigation satellite system) satellites observation data of January 1 to 30, 2017 by means of simulation. The constellation types include 60, 96, 192 and 288 satellites respectively. Based on these data and taking African region as an example, the coverage of GNSS and LEO satellites' ionospheric pierce points and the joint modeling accuracy are studied. The results show that, after LEO satellites are added, the distribution of ionospheric pierce points is significantly improved, which leads to a noticeable rise of their density. The range of ionospheric pierce points of single low-orbit satellite is larger than that of GNSS satellite, and the altitude angle and azimuth angle of LEO satellite change remarkably. With the increase of the number of low-orbit satellites, the accuracy of joint modeling also rises up. Within different latitudes of 30°E at UTC 12:00, the difference between GNSS-only and GNSS+288 LEO ionospheric modeling results is the largest, reaching -1.6 TECU. With the increase of modeling time, the difference between the joint modeling results and GNSS-only results gradually decreases.