Abstract: Abstract: Northeastern China (NC), including Heilongjiang, Liaoning and Jilin provinces, is a dominating area of milk production in China, where is characterized by extremely cold winter under the continental climate. There is a great influence of the walls/roofs thermal resistance on the heat preservation and temperature stability of the dairy barns in this area. However, it is currently lacking of relevant technical references and standards on the thermal resistance for the design of dairy barns. To maintain the indoor temperature at a relatively high level, lots of dairies in this area seldom open the windows and/or openings for the proper ventilation in cold winter, particularly at night, leading to the high relative humidity (RH) and high concentrations of the contaminated gas inside the barns. Consequently, it can hurt the health of the cows, and result in the reduction of milk yield. The purpose of this paper was to determine the recommended minimum thermal resistance (RMTR) of the walls and roofs for dairy barns in NC area using the thermal design method of civil buildings. To verify the calculations of the RMTR values, a field experiment on heifer barn was also conducted during January 25-28, 2016 in Baoqing countryside, Heilongjiang province. Management suggestions on the proper ventilation rates for the surveyed dairy barn were given based on the heat balance model, including sensible heat production, heat loss from ventilation and insulation. The results showed that in the case of the ideal indoor temperature (10℃) and RH (80%), the calculated RMTR of the dairy barns from the southernmost (the city of Dalian) to the northernmost (the city of Mohe) in NC, were in the range of 0.47 to 1.54 m2·℃/Wfor the walls, and 0.63 to 1.97 m2·℃/W for the roofs. These values were comparableto that the required thermal resistance for dairy barns in cold area (<-6.7℃) in Japan, whereas smaller than the general thermal resistance recommended for agricultural structure (including the dairy housing) design in cold area (<-10℃) in US. The designed thermal resistances of the gable/side walls in the barns were about 50.9% and 51.9% of the local RMTR, leading to much condensation and erosion at the internal surface of the walls and thus lowering the inner surface temperature. Furthermore, the actual ventilation rate of the surveyed barns that determined using carbon dioxide (CO2) balance method, was approximately 0.09 m3/(h·kg), much less than the recommended ventilation (0.17 m3/(h·kg)) for dairy barns in winter in this area. The measuring results showed that the indoor RH of 99.1%, the CO2 concentration of 10 538 mg/m3 and the NH3 concentrations of 24.5 mg/m3, were all beyond the thresholds of a healthy environment for the dairy production. In this surveyed dairy barn, a ventilation rate of 0.14-0.15 m3/h per kg body weight of the cow was recommended to keep the indoor RH of approximately 80% and the temperature above 0 ℃. Therefore, the roof vents and chimney fans can be chosen for the improvement of the daytime ventilation, while the proper ventilation should be increased at nighttime, both of which can meet the requirement for the better environmental condition. In the newly-built dairy barns, the thermal resistance should be higher than the RMTR. This study on the RMTR value provides the fundamentals and examples for the construction and refurbishment of dairy barns, and the management of the winter ventilation, as well the improvement of the indoor micro-environment, for the dairy production in cold winter in Northeastern China.