In order to study the effect of wheat straw biochar input on soil thermal properties in fallow period.Three wheat biochar application levels were set up in this study: 0 kg·m-2(BC0)，1 kg·m-2(BC1)and 4 kg·m-2(BC4)，and each treatment was repeated for 3 times，and field plot experiments were carried out.The soil moisture content，heat capacity，thermal conductivity，thermal diffusivity and temperature of each plot were measured.The results showed that the application of biochar significantly reduced the soil thermal conductivity and thermal diffusivity，and the more the application amount，the lower the value of thermal conductivity and thermal diffusivity.The heat capacity was firstly decreased and then increased with the increase of the amount of biochar applied.Soil water content fluctuated greatly by rainfall and freezing，and decreased with the increase of biochar content in the absence of precipitation and freezing conditions，while increased with the increase of biochar content in the freezing-thawing period at low temperature.All the thermal parameters were basically consistent with the variation trend of water content，and the thermal parameters of BC1 and BC4 were significantly positively correlated with water content(P<0.05).The soil temperature in 5 cm section increased firstly and then decreased with the increase of biochar application amount.The soil temperature in the 20 cm section decreased with the increase of biochar application amount.The thermal conductivity and thermal diffusion of all treatments were significantly positively correlated with the soil temperature in the 5 cm section(P<0.05)，and significantly positively correlated with the soil temperature in the 20 cm section(P<0.01).It can be seen that biochar affected the change of soil thermal properties in farmland mainly by affecting water content，and the degree of influence was related to the application amount of biochar.The addition of wheat straw biochar could affect soil temperature in farmland by affecting soil thermal properties.