Abstract: In order to measure the complex slope angle accurately and control the construction precision of slope engineering，a non-contact slope angle measuring device is designed based on the laser distance and video recognition technology.According to the three-dimensional geometric structure，measured parameters and trigonometric functions，the formula for calculating the complex slop angle is deduced.All of the error factors are discussed based on the indicators of the angle measuring device.According to the influence degree of the error factors to the final measuring results，α₂ is regarded as the sensitive factor of the measuring device.According to the fixed error of the laser range finder(ΔL),the calculation formula of pseudo angle is deduced.The influence rule of ΔL to L₁ is analyzed by case research method.The research results illustrate that，the inclination angle error increases with ΔL growing while with L₁ decreasing.The measuring error of slope angle β follows in a positive linear correlation with ΔL.When the value of ΔL reaches to 1 m，slope angle measurement error can be as much as 2.92%.Nevertheless，the measuring error of slope angle β follows in a negative linear correlation with L₁，when the value of L₁ reaches 20 m or 10 m，the maximum slope angle error can be as much as 4.31% or 8.26% accordingly.Therefore，the measuring accuracy of slope angle can be improved by enhancing the accuracy of laser equipment and maintaining the effective distance between laser equipment and slope.

Key words: Slope angle, Laser ranging, Non-contact, Error analysis, Sensibility