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In order to solve the problem of overheating of the engine and cooling system of the vehicle in the plateau low-pressure environment, it is necessary to study air-side thermal-hydraulic performance of the vehicle cooling system heat exchanger under low-pressure environment. In this paper, the experimental study on the louvered fin and flat tube heat exchanger of the vehicle is carried out on the low-pressure wind tunnel test bench. The results show that at a gauge pressure of −44 kPa, the air-side convective heat transfer coefficient is reduced by 33.5%~23.3% compared with 0 kPa; the Colburn j-factor is increased by 36.8% on average; the f factor is increased by 51.2% on average. Based on this, numerical simulations are carried out to study the heat transfer and flow characteristics of louvered fins with different structural parameters under low-pressure environment. The empirical correlations of Colburn j-factor and Friction factor f are fitted by multiple linear regression. In the range of gauge pressure from 0 kPa to −44 kPa, the average deviation of the correlation calculation result of Colburn j-factor is 3.4%, and the average deviation of the correlation calculation result of f factor is 5.5%. The research results can provide a basis for the design of louvered fin heat exchangers utilized in the plateau environment. [ABSTRACT FROM AUTHOR]