Secondary metabolites of endophytic fungi FSN002 from Juglans mandshurica Maxim have excellent liver cancer resistance. Preparation of mutant strains is an important means to study the biosynthesis mechanism of catalitaxol. Fungal spores germinating young hyphae with 4 to 6 cells after culturing for 13 hours were used as starting materials of ultraviolet (UV) mutagenesis. UV light intensity and irradiation time have a linear relationship with fungal mortality. The two factors had no obvious interactions. When UV light was 90 000 μJ/cm2 and irradiation time for 6 s, the mortality of fungi was around 95%. Under the optimization mutation condition, two mutant strains were obtained, of which one lost the synthesis ability of catalitaxol completely, and the another synthetized only 16% catalitaxol of the wild strain. Our findings may serve basis for further study on the biosynthesis mechanism and efficient production of catalitaxol.