Five new alkaloids together with 20 known ones were isolated from Alstonia rostrata, and identified on the base of NMR, MS, UV and IR spectroscopic data. Additionally, alstrostine G (1) possessed an unprecedented 6/5/6/6/5/6-ring system. The analysis of those alkaloids' biosynthetic pathway partly indicated their reticulate metabolic relationship. The research result disclosed diverse biogenesis of monoterpenoid indole alkaloids from Alstonia rostrata speciesin combination with previous reported alstrostine A.