Microwave-assisted temperature-controlled ultrasonic extraction was used to extract total alkaloids from stem of Euchresta tubulosa Dunn. The extraction process was optimized by single factor method and response surface methodology. The scavenging effects of total alkaloids on 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH•), 2,2-diazo-2-3-ethyl-benzothiazole-6-sulfonic acid (ABTS•) and superoxide anion (O2－•) free radicals were investigated. The results showed that the optimum conditions were as follows: extraction time 37.8 min, microwave heating temperature 64.5℃, ultrasonic power 575 W and ethanol volume fraction 95%. Under these conditions, the yield of total alkaloids was 0.5436%, higher than no microwave-assisted ultrasound 0.2436%, ultrasound assisted 0.4538% and ethanol reflux 0.3884%. When the concentration of the extracted total alkaloids was 0.1, 7.0 and 8.0 mmol/L in DPPH•, ABTS• and benzene-1,2,3-triol, respectively, the corresponding half maximal inhibitory mass concentrations (IC50) were 0.891, 0.552 and 0.390 g/L.