The invention relates to the technical field of agricultural production and in particular relates to a flue-cured tobacco maturity field investigation and quantitative forecast method for determiningsuitable harvesting period of tobacco. The method comprises the following steps: dividing a tobacco field into at least one type; dividing at least one representative monitoring field piece in each ofthe types of the tobacco field; selecting at least one representative sampling point in each representative monitoring field piece; selecting 8-12 tobacco plants as investigation plants at each representative sampling point, and performing tobacco maturity investigation, wherein the maturity investigation comprises counting mature leaves of each investigated tobacco plant and counting suitable harvesting tobacco amount of all tobacco plants in each type of the tobacco field in each baking round when green color of the tobacco starts to fade in the first round and before the tobacco is mature;and comparing the suitable harvesting tobacco amount with single one-baking suitable tobacco filling amount. According to the method, the quantity of mature tobacco leaves in the field can be accurately mastered, each batch of the mature tobacco leaves can be appropriately harvested at the right time, and the problem that mature tobacco harvesting is difficultly realized is solved immediately. Therefore, the tobacco production is specialized and accurate.