Abstract: Taking S. miltiorrhiza variety "Tiandan 1" as the test material, pot inoculation method and field plot experiment were adopted to study the inhibitory effect of a series of concentrations of walnut green husk extract(50 mg/mL, 100 mg/mL, 150 mg/mL, 200 mg/mL and 250 mg/mL) on the pathogen of S. miltiorrhiza root rot and its field control effect. The results showed that:(1) The walnut green husk extract had a significant inhibitory effect on the pathogen of S. miltiorrhiza root rot, and the inhibitory effect increased with the increase of mass concentration. The indoor antibacterial rate of 250 mg/mL concentration treatment reached 82.38%.(2) In the pot experiment, the control effects of 200 mg/mL and 250 mg/mL concentration treatments were 70.02% and 80.25%. In the field experiment, after 3 applications, the 250 mg/mL walnut green husk extract treatment had the highest control effect, reaching 83.76%, which had no significant difference from the 50% carbendazim 800-fold liquid treatment(84.86%).(3) The walnut green husk extract biopesticide had significant promoting effect on the growth of S. miltiorrhiza, and could increase the growth indexes such as plant height, stem thickness, main root length and fresh root weight, as well as the yield of S. miltiorrhiza. This study indicates that walnut green husk extract is a high-quality biopesticide for controlling S. miltiorrhiza root rot, and 200~250 mg/mL is the suitable application concentration, which can provide a new approach for the green control of S. miltiorrhiza root rot.