The particle accumulation structure is commonly found in diverse engineering fields, including additive manufacturing powder, powder metallurgy, advanced reactor, grain storage and catalyst bed. The relative thermal conductivity of such structure is an important parameter to study the heat transfer behavior of the accumulation. In the study, the key factors affecting on the thermal conductivity of the powder is analyzed. Based on the results, the expression for calculating the thermal conductivity of the sphere metal powder is successfully reduced to only one parameter d50 and an efficient calculation model is proposed which can applicate both in room and high temperature. Meanwhile, the corresponding error is less than 20.9% in room temperature and 50% in high temperature.