Abstract: The chemical constituents of Alnus nepalensis were studied and seventeen compounds were isolated by the method of silica gel column chromatography and recrystallization.Their structures were elucidated as Lupeol(1),Betulin(2),(6aR,8aR,12bR,14bR)-1,2,4a,5,6, 6a,8a,9,10,11,12,12a,12b,13,14,14a-hexadecahydro-4,4,6a,8a,11,11,12b,14b-octamethylpicen-3(4H,8H,14bH)-one(3),lupene(4),nepeticin(5),betulinic acid(6),-sito-sterol(7),daucosterol(8),-rosasterol(9),alpinetin(10),pinocembrin(11),2,3,4,5-tetrahydroxypentanal(12),isovanillin(13),2-hydroxymethyl-phenol(14),2,3,4,5-tetrahydroxy-hexanal(15),gallic acid(16),sterols stigmasterol(17) by the means of spectral data analysis and comparison with the reported data and standard sample.The structure of compound 2 and compound 3 was also confirmed by X-ray diffraction for the first time.