The oxygen supply and ventilation of high altitude tunnel in low pressure and low oxygen environment are very important. The field test and monitoring methods are adopted; the hypoxia situation of construction personnel, oxygen supply effect and mechanical pollution of high altitude tunnel are studied; and theoretical reduction and numerical calculation are carried out. Some conclusions are as follows: 1) The hypoxia of construction personnel can be divided into 4 grades, i. e. serious hypoxia (Grade Ⅰ), ordinary hypoxia (Grade Ⅱ), potential hypoxia (Grade Ⅲ) and non hypoxia (Grade Ⅳ). 2) The CO volume fraction models in different altitudes are obtained. 3) The calculation formula for air duct leakage rate based on altitude correction coefficient are deduced by air flow theory at air duct opening. 4) The altitude correction coefficient formula for air pressure and power of fan is obtained. 5) The labor intensity index and grade in different altitudes considering average energy metabolism rate based altitude correction coefficient are obtained.