The invention provides a helical angle measurement method of a helical tapered gear. A linear distance of helical lines AB is measured and a helical angle can be calculated according to a corresponding relation between the gear and a tool parameter. The helical angle measurement method utilizes simple measurement tools including a height gauge, a vernier caliper and the like, and measurement steps are simplified; a parameter relation between the helical tapered gear and a tool is sufficiently utilized and the helical angle with the higher accuracy is calculated; the helical angle at any position can be measured.