In order to explore the effects of biochar application on soil moisture storage, heat preservation and fertilizer conservation in saline soil during freezing-thawing period, taking saline soil as the research object, in situ freezing-thawing tests of field plots were carried out in the Hetao Irrigation Area for two consecutive years, the biochar dosages were set as 15 t/hm² (D15), 30 t/hm² (D30) and no biochar (CK). The results showed that under the freezing-thawing conditions, the vertical distribution of water in 0—40 cm soil was more obvious than that in 40—100 cm soil, and the water storage capacity was greater. In addition to the decrease of soil water storage at 0—40 cm by applying biochar in the initial freezing period of the first year of experiment, the water-holding effect of biochar gradually appeared with the increase of application time. Compared with CK, D30 treatment was more beneficial to soil water retention. Applying biochar could suppress the variation of soil temperature in freezing-thawing period and reduce the dispersion degree of soil temperature change in thawing period. Compared with the control, the average soil temperature of 0—40 cm in the freezing-thawing period of 2 years was increased by 0.8~1.6 ℃ under biochar treatment. After two years of freezing-thawing, the soil freezing index of each treatment was CK > D15 > D30, and the melting index was D30 > D15 > CK. In the freezing-thawing period, the application of biochar enriched the soil nutrient content and reduced the soil nutrient loss from 0 cm to 40 cm in various freezing-thawing stages. The contents of available K, alkali-hydrolyzable N and available P increased by 3.1%~38.1%, 1.3%~44.6% and 5.4%~80.4%, respectively. Organic carbon density increased by 2.0%~22.4%, and D30 treatment had the most obvious improvement effect. The application of biochar improved the hydrothermal fertilizer status of saline soil in freezing-thawing period, and provided a good environment for the growth and reproduction of crops in the next year. The application effect was better when the amount of biochar was 30 t/hm².