For comparing the selective toxicity of chlorfenapyr between silkworm and mulberry silkworms and mulberry pests, the toxicity of chlorfenapyr, diazinon, dichlorvos, phoxim and triazophos was determined using food intake method, the toxicity of the five insecticides to Phthonandria atrilineata Butler, Diaphania pyloalis Walker and Porthesia xanthocampa Dyer was assayed in room using leaf dipping method, the period of residual toxicity of chlorfenapyr on mulberry to silkworm was tested by spraying pesticide in mulberry field, and the effect to growth and development of silkworm was investigated using food intake method. The results indicated that the toxicity of diazinon, dichlorvos, phoxim and triazophos in 72 h after treatment was 15.5, 93.3, 154.0 and 188.5 times higher than that of chlorfenapyr, respectively. The LC₅₀ of chlorfenapyr, triazophos, phoxim and dichlorvos in 48 h after treatment to P. atrilineata was 49.1, 3.2, 2.3 and 1.4 times higher than that of diazinon, to D. pyloalis was 79.4, 3.6, 2.4 and 1.8 times higher than that of diazinon, and to E. similis was 67.2, 3.2, 2.2 and 1.7 times higher than that of diazinon, respectively. The period of residual toxicity of 100, 50, 25 and 12.5 mg/L of chlorfenapyr sprayed on mulberry field was 3, 0, 0 and 0 days, respectively. The developmental duration of survival larvae, the weight of dormant silkworm, the weight of mature silkworm, cocoon weight, cocoon shell weight, pupa weight and pupation rate in treatments of 100, 50, 25 and 12.5 mg/L of chlorfenapyr showed no significant difference compared with the control. The results suggest that chlorfenapyr is an insecticide suitable to control pests in mulberry field and safe to silkworm.