Taking Dabao (from Dali city to Baoshan city) and Sixiao (from Simao city to Xiaomengyang town) highways in longitudinal range-gorge region as examples, the biomass of different vegetation types (arbor, shrub and herbage) on the sampling points (the distances to road are 5m,20m,40m,80m,120m and 200m respectively) and their contradistinguishing points under different landforms were measured on spot.The affecting characteristics and intensities of highway construction on plant biomass of all sampling points were analyzed by contrasting the measured values(between the sampling points and their contradistinguishing points).The function equations of plant biomass changing with the distances from road were simulated with method of regress analysis, then the affecting scopes of highway construction were identified.The affecting intensities and scopes of the two roads under different landforms on biomass of different vegetation types were also compared in this paper. The conclusions are as follows: 1)Highway construction affects plant biomass of roadsides through changing the quantities of green vegetations and plant photosynthesis. It’s impacts include two types,the impacts on arbor are mainly negative while the impacts on shrub and herbage are mainly positive.2) the curves of arbor biomass changing with the distances from road present form “J", with their maximum values of all the sampling lines located at the most distant sampling points,while their minimum values located at the nearest sampling points.The curves of shrubs and herbages present “singe apex" form, their maximum values are located at the points which are 20～50m distant from road.The plant biomass values of the sampling points which are very close to or faraway from road are lower,while the minimum values located on the sampling points which are 120～200m distant from road.3)Effect caused by the two selected highways on plant biomass differ greatly in the affecting scopes and intensities due to their different sections and landforms.Dabao highway has the higher affecting scopes on all vegetation types along the road than Sixiao highway.As for Dabao highway has higher impacts on arbor than Sixiao highway in comparison with the lower impacts on shrub and herbage than the latter. The compared results of affecting scopes and intensities between the two different landforms meet the following order: mountainside > mountaintop, while affecting scopes among different vegetations are:herbages> shrub>arbor, and the affecting intensities are: arbor >shrub> herbages.