To optimize extracting process of flavonoids from Senecio cannabifolius Less. Methods： The ultrasonic time， the optimum extraction conditions and the material ratio were investigated by single element experiment; the optimum extraction conditions were investigated by orthogonal design and with flavonoids from Senecio cannabifolius Less as the content index by Uv results. Results： The best optimum extracting condition was under 70% ethanol， material ratio 22：1， and extracting time lasting for 150 mins. Conclusion： The method is simple， convenient and can be controlled easily， and suitable for the determination of Senecio cannabifolius Less.