Abstract: Comparison of photosynthetic characteristic and essential oils in crop rotation and continuous cropping of Angelica sinensis was studied to explore the influence factor of dropping the yield and quality after continuous cropping, this conclusions will provide theoretical basis for investigation of continuous cropping obstacle of A. sinensis. Chlorophyll, photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO₂ concentration of A. sinensis were measured with CI-310 photosynthesis system. The yield and constituent of the essential oils extracted from the A. sinensis. Water steam and GC-MS were used. Chl a and Chl b of continuous cropping dropped apparently, at 26.5% and 57.0% less than rotation one, and the differences were significant(P<0.01); Daily mean photosynthesis of continuous cropping was 1.73 μmol/(m²·s), less than rotation (2.61 μmol/m²·s) by 50.9%, the differences were significant(P<0.05); In a day, transpiration rate in the morning was significant lower than that in the afternoon, the continuous cropping was significant lower than the rotation one. The difference of stomatal conductance average between rotation(11.4 mmol/m²·s) and continuous(10.6 mmol/m²·s) was not significant before 12:00,but had extremely significant difference between continuous(1.3 mmol/m²·s) and rotation(4.4 mmol/m²·s); Intercellular CO₂ concentration had the same variation. The yields of the essential oil of A. sinensis in crop rotation and continuous cropping are 0.95% and 0.70%, The relative amounts of ligustilide of essential oil are 71.62% and 29.49%. but the constiuents of the essential oil of A. sinensis from crop rotation and continuous cropping are identical. Continuous cropping decreased significantly the Chl, photosynthetic characteristica and essential oil of A. sinensis, which resulted in yield decreasing. Therefore Angelica contivation should think rotation low-toxin chemical.