The invention provides a road three-dimensional linetype modeling method and system. The method comprises the steps of dividing a road into a plurality of road sections according to flat and vertical combinations, and taking start and stop points of the road and connecting points of the adjacent road sections as control points; obtaining three-dimensional coordinates, Frenet coordinate frames and curvatures at the control points, and taking the three-dimensional coordinates, the Frenet coordinate frames and the curvatures at the control points as geometric constraints at the control points; converting the geometric constraints at the control points into parameter constraints by utilizing a method for converting the geometric constraints into the parameter constraints, and obtaining a sectioned polynomial expression of a road central line meeting the geometric constraints at the control points; and obtaining three-dimensional coordinates of any point on the road central line according to the polynomial expression. According to the method, a three-dimensional linetype of original combination design is replaced with a unified spline curve, the three-dimensional essential property of the road linetype is obeyed, and an original design process can be greatly simplified.