Abstract: In order to study the oxygen concentration issues in the case of workers working in high-altitude tunnels, riding tests were carried out to get the physiological indexes and the labor intensity indexes of test objects at the altitude of 590~4 000 m and oxygen concentration of 20.9%~29% under the riding loads of 0, 50 W, 75 W and 100 W.The analysis and research conclusions are as follows: (1) under the working conditions of the same altitude and the same labor intensity, increasing the ambient oxygen concentration can significantly reduce the labor intensity index;(2) there is no linear relationship between the decrease of labor intensity index and the increase of oxygen concentration. When the ambient oxygen concentration exceeds 25%, the decrease of labor intensity index is limited; (3) the relationship between the labor intensity index of construction workers and the altitude and oxygen concentration is fitted and obtained under the labor load of 100 W and the oxygen concentration of 20.9%~25%.