Two new natural ecdysteroids, 20,22-didehydrotaxisterone (1) and 1-hydroxy-20,22-didehydrotaxisterone (2), were isolated from the roots of Serratula wolffii. Their structures were elucidated by 1D and 2D NMR spectroscopy and mass spectrometry. The biological activities of these compounds were determined via oral aphid (Acyrthosiphon pisum (Harris)) tests. Compound 1 was inactive and compound 2 exhibited very low toxicity in the oral aphid test. The activities of these two ecdysteroids were in agreement with those of other 22-deoxyecdysteroids.