The miticide activity of Paecilomyces farinosus strain nq1–1 to Panonychus citri(McGregor) was determined by the method of indoor toxicity, and single factor tests were used to explore the biological characteristics of the strain. The results indicated that the LC50 and LT50 of strain nq1–1 to Panonychus citri(McGregor) was respectively 1.59×107 /mL and 7.9 d. SDAY and PDA medium were both the optimum mediums to strain nq1–1 for hyphal growth and sporulation. Sucrose and lysine were conducive to fungal growth and sporulation. The most suitable culture temperature for hyphal growth and sporulation were 20 ℃, and temperature at 25–28 ℃ was most conductive to the spore germination. The optimum pH for hyphal growth, sporulation and spore germination was 6.0. UV had no significant effect on strain nq1–1. Moreover, strain nq1–1 had a good compatibility with 82.6% cuprous oxide WG, 75% chlorothalonil WP, 50% oxine–copper WP. In conclusion, strain nq1–1 was toxic to Panonychus citri(McGregor), and grew best under slightly low temperature, neutral pH and high organic nutrition.