Effect of five decapitation treatment of the first topping time for the bud of the day, after squaring 5 d, 10 d, 15 d, 20 d. were studied on flax anti-lodging, yield and quality . The results showed that from the budding stage to the day after budding 20 d, with the topping over time, the field lodging rate increased from 4.5% to 26.5% and lodging degree aggravated appropriately, while its vertical hemp plants reduced from 90.5% to 65.5%; its height and process length increased from 70.5 cm to 80.5 cm and stem diameter decreased from 0.262 cm to 0.240 cm. Stem yield of budding 5 d and 10 d after decapitation treatment reduction (4.45% - 5.64%) had no obvious change, but other treatment reduced significantly compared with control. The fiber quality of topping treatment in different time was improved; its single fiber strength reinforced 19.72% - 34.25% and the degree of fiber splitting increased 2.24% - 5.88%. Therefore, from the field lodging and the yield into account, the optimum decapitation time treatment should be 5 - 10 d after budding at the later growth stage.