Abstract: In order to study the effects of biochar application on soil structure, water holding capacity, maize yield and sustainability of sloping farmland in black soil area, four consecutive years of biochar effect experiments were carried out in the runoff plot of 3° sloping farmland in black soil area from 2015. A total of five biochar application rates C0（0 t/hm~2）, C25（25 t/hm~2）, C50（50 t/hm~2）, C75（75 t/hm~2） and C100（100 t/hm~2） were set. The results showed that soil bulk density was decreased with the increase of biochar in the four years, and porosity was increased gradually. Appropriate amount of biochar can effectively reduce the proportion of soil solid phase and improve the proportion of gas phase and liquid phase. In addition to 2015, the generalized soil structure index（GSSI） was increased first and then decreased with the increase of biochar application rate for three consecutive years, and the three-phase structure distance index（STPSD） was decreased first and then increased with the increase of biochar application rate, reaching the optimal values（99.96,0.63） in the third year of C50 treatment. At the same time, the soil three-phase ratio R was the smallest（1.03）, and the three-phase ratio was the closest to the ideal state. For four consecutive years, the aggregate content R_0.25, mean mass diameter（MWD） and geometric mean diameter（GMD） were increased first and then decreased with the increase of biochar application rate. Adding 50 t/hm~2 biochar for three consecutive years had the best effect on improving soil stability. The saturated moisture content was positively correlated with carbon application rate for four consecutive years. In addition to 2015, the field water holding rate was increased first and then decreased with the increase of carbon application rate, and reached the optimal treatment at C100, C50, C50 and C25, respectively. The peak value was 37.33% at C25 in 2018. The change rule of soil effective moisture content and field water holding capacity was the same. Soil water storage in 0～60 cm soil layer of maize at different growth stages was increased first and then decreased. Soil water storage in 60～100 cm soil layer was negatively correlated with carbon application rate. The maize yield sustainability index（SYI） reached the maximum at C50（0.954）, and the coefficient of variation（CV） was the lowest at C100（0.022）. Annual application of 50 t/hm~2 biochar to promote maize yield stability and sustainability effect was the most obvious.