Abstract: Based on the data of field plot experiments and meteorology during the harvesting time in Xi'an,the influence of meteorological factors such as precipitation and temperature,on the yield and quality of the essential oil of the Scotch Spearmint was studied.The results showed that precipitation and temperature during harvest time strongly influenced yield of essential oil of the Scotchish Spearmint.The rate of essential oil extraction and the essential oil yield were negatively related to the precipitation.The heavy rain might lead to reduction of the essential oil yield by 50%.However,if there was three to five fine days,the same rate of essential oil extraction and the essential oil yield could be got as that before the heavy rain.The rate of essential oil extraction and the essential oil yield were positively related to the temperature during harvest time,in particular as the daily average temperature above 20℃.The appropriate harvest time of the Scotch Spearmint was with continuous three fine days and the daily average temperature above 20℃.

Key words: Meteorological factors, Meteorological factors, Scotch Spearmint, Yield, Quality