The invention relates to a combined optimization method for simplifying digital map linear factors, which can effectively solve the problem of keeping data precision when simplifying linear factors while satisfying GIS display and map charting output effect. The method comprises the following steps: qualitatively and quantificationally estimating the redundancy degree of the curve; calculating geometric information volume on each point of the digital curve by a mathematical model measured by point location geometric information; determining a larger point to a curve feature point, wherein a head end point, a tail end point and the feature point on the curve are critical points which divide the curve into a plurality of monotonic segments; after adopting an improved Li-Openshaw method to simplify each monotonic segment for several times, simplifying each divided monotonic segment by section with a Doulas-Peucker method; evaluating a simplified curve by the evaluation model of the curve simplifying result; and outputting simplified linear factor data. The invention has strong universality and favourable effect and improves the production efficiency and the product quality of the digital map and a paper map.