The geological condition of highway engineer in karst mountain area is very vulnerable.It is easy for landslides development along the whole or part of the slope.Therefore

it is very necessary to locate and monitor the potentially unstable slopes along the highway in order to ensure the operational safety in the mountainous area.This study selected an unstable roadside slope in a typical karst mountain area in Jiuxiang

Yunnan Province as the monitoring object.Aiming at the shortcomings of the traditional"point"monitoring method

this paper adopted the surface Terrestrial Laser Scanning（TLS）technology to carry out field scanning on the slope and got the 3D point cloud data of the slope surface.On the basis of the I-Site Studio 3D point cloud data processing platform

the authors preprocessed the 3D point cloud data obtained from the slope scanning

including the registration of point cloud data

filtering and denoising

and cavity repair.Besides

the experiment and research on fine modeling and 3D scene construction were carried out.This research established a comprehensive technology application process including the use of surface TLS technology to collect 3D point cloud data

3D data preprocessing and 3D scenario construction in the mountainous area.In addition

the accuracy of the TLS technology used in the slope monitoring of the experimental area was evaluated.The research results show that

compared with the traditional"point"monitoring method

the surface TLS technology can get more abundant spatial 3D data in slopes monitoring along the highway in the karst mountainous area

and build a refined 3D scene model.