The evaluation on labor intensity of workers in Guigala Highaltitude Tunnel is of great significance. Hence, the workers in the entrance section(4 300 m above sea level) and inclined shaft No.1 section(4 560 m above sea level) of Guigala Tunnel are selected as test objects, and the physiological function indices of the workers in different working procedures, such as heart rate, blood oxygen saturation, oxygen consumption, etc., are measured. And then the energy metabolism rate is calculated based on oxygen consumption, and the labor intensity index of each procedure is further calculated. The test results show that: (1) The difference of comprehensive labor intensity indices caused by altitude difference of 260 m has statistical significance （P<0.05）. (2) The labor intensity at the construction procedure of steel bar binding of secondary lining is the highest, the physiological function indices of the workers exceed limits, and the labor intensity index reaches 35 (extremely heavy). (3) In the range of 4 300-4 560 m above sea level, the labor intensity of each construction procedure of Guigala Tunnel is mostly between moderate and extremely heavy.