This research aims to identify the optimal harvesting time of Mesona Chinensis Benth. In Trang Dinh district, Lang Son province in the spring and summer-autumn crop in 2019. A completely random block arranged the experiment with three repetitions. The experiment on harvesting time includes five formulas: 90 days after planting, 100 days after planting, 110 days after planting, 120 days after planting, and TH5 130 days after planting. Planting density is 100,000 plants/ha (50 x 20 cm). Research results indicated that the harvesting time of 120 – 130 days after planting in spring and summer-autumn gives the highest quality, yield, and economic efficiency. Specifically, polysaccharide content is 0.41 – 0.42 (OD 1/25); Viscosity amount is 4.3 – 4.4 cP; Pectin content is 0.41 mg/ml; Ash content is 6.28% - 6.48% and leaf yield reaches 59.33 – 61.67 tons/ha in spring and summer-autumn, respectively.