First, the spearmint currently used for production has two varieties, big leaf and small leaf. The ripening period (flowering period) of spearmint is related to the characteristics of varieties and climatic conditions. Therefore, the determination of the harvest time in each place should be flexibly controlled according to local conditions. Generally speaking, the flowering period of S. splendens is earlier, and the large-leaf spearmint is later. The harvest is usually carried out from the flowering stage to the flowering stage, and it is harvested 2 times a year. In some places in the south, it may be received 3 times. However, comprehensive consideration must be taken in terms of output, quality and cost. Regardless of whether it is harvested 2 or 3 times a year, the last harvest must be carried out before the frost falls, otherwise the oil rate will drop sharply as the temperature decreases. The fresh grass that is cut off should be dried to a half-dry (ie more than 50% of the water loss of the fresh material) and then distilled. This will not only save fuel and labor, but also increase the oil yield and improve the quality of the essential oil. Second, the length of processing and distillation is one of the factors affecting the aroma of spearmint oil, distillation time is too long, the aroma is poor. Therefore, in the production must strictly control the distillation time, generally 1 cubic meter volume of distillation pot for 1.5 to 2 hours. Spearmint oil distillation according to the fresh weight of oil rate of 0.3% to 0.4%.