Abstract: Abstract: The first low profile cross ventilated (LPCV) dairy cattle barn was built in fall 2005 in North Dakota. The barn is generally a fully enclosed facility characterized by a low roof pitch of 0.5/12 and a warehouse-type structure. It was introduced to China in 2009 and since that time several barns have been built in large dairy farms in China as a newly-developed dairy cattle barn type. The LPCV barn offers some of the advantages of natural ventilated and tunnel ventilated freestalls and allows producers to have some control over the cow's environment during all seasons of the year. But in China there are technical bottlenecks for environmental control problems in operation, including uneven distribution of indoor airflow, high-temperature and high-humidity in summer, low-temperature and high-humidity in winter et al. The use of computational fluid dynamics (CFD) techniques to solve complex fluid problems has greatly increased in recent years. In this study, a full-scale dairy cattle house was modelled to investigate the distribution pattern of airflow in LPCV barn. The simulation of dairy cattle was considered to improve the reliability of the CFD model, as the presence of cows in barns can significantly influence air flow patterns and internal environmental conditions. The evaporative cooling pads on the air intake side of the barn were considered as porous media and the coefficients of the viscous and inertial resistances were determined by laboratory values. The performance curve of the exhaust fans on the air outtake side was measured in laboratory to establish the boundary conditions of the fans. Baffles are located over stalls in LPCV barn to increase air velocity in each freestall area. Simulation results shows that the problem of uneven flow distribution is generally exist in the barn. The wind speed differed greatly between the two sides of the baffle in the bedding area. The wind speed was significantly lower for the windward side compared with the other side. The main reason for the uneven flow distribution in the barn was the parapet below the neck rails. If there is no parapet, the average wind speed could increase by 60.6%, and the air uniformity coefficient could decrease by 68.7%. For the existing LPCV barn, keeping the baffle wall and the parapet unchanged, the air flow could be improved by the installation of a baffle on top of the neck rails of the windward of the feeding alley. The modification has a significant effect on the airflow distribution improvement, with the averaged wind velocity increased by 52.8%, the airflow uniformity coefficient decreased by 41.8%. The CFD model was validated via comparison with the field experimental results at the same locations where the sensors were installed. Comparison between simulations and measurements showed that the average relative error of the test and simulated value for the 28 test points was 17.1%, which indicates that there is a goodness of fit between field measurement and numerical simulation. And this study can provide references for the optimization design and environment regulation of LPCV dairy cattle barn in China.