With 16 years old Larix kaempferi plantation in eastern mountain area of Liaoning Province as test object, this paper studied its total fine root biomass, fine root biomass at different soil depths, and biomass of different root orders under effects of fertilization. The results showed that compared with no fertilization, applying N decreased the total fine root biomass significantly (P 0.05), except the fifth order root in treatment P, and the second order root in treatment P + N (P 0.05), while treatment N + P increased the first order fine root biomass significantly (P < 0.05).