While road construction should facilitate regional socio-economic development,it also imposes impact on the surrounding ecosystem by directly changing the original ecosystem and indirectly enhancing the intensity of human activities.Quantitative assessment of the road construction impact on the net primary productivity (NPP) of vegetation has a certain practical significance for grasping the ecological and environmental influence of linear engineering and weighting the socio-economic development and ecological safety.Based on the road data of 2016 and NPP data of 2015 in southwest China,this study used kernel density (KD) to represent the road-effect zone and influence intensity and analyzed the relationship between road construction and NPP under different land cover and economic development intensity with the help of ArcGIS platform.The results show that:(1) when the search radius is 0.5 km,the road KD ranges from 0.0 to 47.3,and the areas where road KD is zero account for around 79.8% of the total research area.Most the undisturbed areas are located in Tibet,Qinghai,and western Sichuan,Guizhou,and northwest Yunnan.The areas where road KD ranges from 0.0 to 5.0 account for around 88.4% of the non-zero road KD areas.Except for cities such as Chengdu,Chongqing,Guiyang,Nanning,and Kunming,the road density in most regions are still at a low level.(2) In terms of the relationship between road KD and NPP under different land cover,forestlands,croplands and built-up lands are more stable under low and medium road disturbance conditions,and NPP is relatively constant when road KD is less than 4.1.However,NPP has changed sharply under the land cover types of grasslands,wetlands and others when road KD is greater than 2.1.With the increase of road KD,NPP tends to diverge,which may be caused by the diversification of different human disturbances on both sides of the road with the increase of road density.(3)Take county administrative divisions as units,the research is divided into 5 zones according to the road KD of per unit area,which gradually increases from zone 1 to zone 5.In zone 1,the NPP increases volatility with the change of road KD,and then decreases and diverges after the relatively stable change;In zone 2 to zone 5,with the increase of road KD,NPP generally shows a decreasing trend,and its variability increases gradually,and it has gone through three stages:relative stability,linear change and divergence.According to the results of this study,road construction should focus on the protection of vegetation in ecologically sensitive and vulnerable areas,such as grasslands and wetlands,and avoid the degradation of the ecosystem caused by high-density road construction as much as possible,and formulate appropriate protection schemes according to different regions.