[Objective] The influence of biochar additions on water storage and water retention capacity of loessial soil during the rainy season was clarified in order to provide basic theoretical support for the scientific use of biochar and to improve soil on the Loess Plateau and determine the reasonable amount of biochar application.[Method] A multi-layer integrated soil moisture-temperature measurement system (JDTS-01) was used to make fixed point observations of soil moisture in a Loess Plateau field. The measured data were corrected by the field correction method. The dynamic change, recharge, and regression of water in the 0-40 cm soil layer were studied. Bivariate correlation analysis was conducted to determine the influencing factors and the relative importance of soil water recharge and regression under different levels of biochar addition.[Results] ① Low biochar content increased deep soil moisture, while high biochar content increased surface soil moisture. On the whole, biochar additions increased soil moisture content. A biochar content of 2.5% may be the inflection point affecting soil water infiltration and evaporation. ② After the addition of biochar, the water content in 0-20 cm soil layer increased, and the water content in 20-40 cm soil layer decreased. The water addition occurring due to rainfall could largely remain in the soil surface layer, and this effect on surface soil water content was greater when the biochar addition was larger. Water in the 0-20 cm soil layer with biochar dissipated faster, while the water in the soil without biochar penetrated deeper into the soil layer. ③ The addition of biochar can promote soil water recharge and weaken soil water regression, thereby increasing loessial soil water storage after rainfall.[Conclusion] Biochar additions can improve loessial soil water infiltration characteristics, reduce deep infiltration of soil water, and increase soil water storage in the topsoil on the Loess Plateau. These effects of biochar additions were more significant when the addition levels were greater than 4%.