Objective: To study the chemical constituents of Petasites japonicus. Method: Mutiple kinds of column chromatographies were used in the isolation procedure. The structures of the isolated compounds were elucidated by spectral methods. Result: Nine compounds were isolated from P. japonicus

including mucusoside (1)

dihydrodehydrodiconiferyl alcohol (2)

n-butyl acetylglutamate (3)

uracil (4)

3α

6α-dihydroxyeremophilenolide (5)

petasiphenol (6)

caffeic acid (7)

β-sitosterol (8)

β-daucosterol (9). Conclusion: Compounds 1-4 were isolated from genus Petasites and P. japonicus for the first time.