Track terramechanics, of which the track stress distribution is the bottleneck, plays an important role in the areas of track mechanism’s design, optimizing, control and simulation. Semi-empirical method and soil trough experiment were combined. Soil shear flow and distribution of slip line during the movement of track mechanism were analyzed on the basis of KARAFIATH concept. The algorithm of amount of soil loss caused by slip, which was used to correct the traditional track-terrain stress distribution model, was raised. Sinkage data of track gathered from soil trough experiment was input to the established model, and then the distributions of normal and shear stresses were obtained. The experimental system of track mechanism—soil interaction composed of soil trough and track-type trolley device as well as its supporting driving element and real-time test system through which can obtain parameters such as driving moment of the motor, horizontal displacement of trolley, sinkage in the traveling process of the trolley, inclined angle of the vehicle body, and motor speed, as well as the variation from the start to the smooth operation of the trolley device was designed and constructed according to the new test system of soil bin developed by the Key Laboratory of Bionic Engineering of Ministry of Education. Laser range finder was constructed with turnplate to realize the stage extraction of shape of track not in contact with a road wheel. The vehicle load, track width and slip rate were taken as experimental factors, the mechanism sinkage was taken as experimental index, and orthogonal experiment design method was adopted. The relative error between numerical calculation and experiment results of normal stress in vertical direction of track mechanism was less than 15%, and correlation coefficient was equal to or more than 0.83 when the weight was 6kg and slip rate was varied from 0.23 to 0.71. The stress model can be used to build mathematical model of interaction between tracked vehicle and terrain.