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In order to explore the effects of biochar on soil water retention, soil nutrients and soybean growth in the black soil area, a four-year observation experiment was conducted on the runoff plot of 3° sloping farmland in the northeast black soil area. In 2015, C0 (0t/hm2), C25 (25t/hm2), C50 (50t/hm2), C75 (75t/hm2), and C100 (100t/hm2) were set according to the amount of biochar applied. For each treatment, the same amount of biochar was continuously applied in 2016, 2017 and 2018. The results showed that the soil water storage in the 0~60cm soil layer was increased and then decreased with the increase of carbon loading for four consecutive years, but the effect on water storage capacity in 60~100cm soil layer was not significant. The saturated water content was increased gradually with the increase of carbon application. In 2015, the water holding capacity and the coefficient of wilting was increased gradually with the increase of carbon application. The growth rate was decreased first and then decreased from 2016 to 2018;applying biochar for four consecutive years increased the plant height and leaf area of soybean growth stages. The optimal treatments were C75, C50, C50 and C25 respectively;the canopy coverage and charcoal content of the four consecutive years showed a parabola change (R2>0.89, P<0.01). The continuous increase of C50 treatment for two years had the largest increase in each growth period, which was 81.4%, 36.7%, 31.5% and 39.6% higher than that of C0. The soil pH value, organic matter and available potassium content were increased gradually with the increase of carbon application for four consecutive years. The alkali nitrogen and available phosphorus were increased first and then decreased. The relatively better fouryear treatments were C50, C50, C25 and C25. The comprehensive fertility index calculated by the improved Nemerow index model was positively correlated with yield (R2=0.8615, P=0.0012, RMSE was 0.75). The biochar application mode with the highest level of soil comprehensive fertility was summarized, that was, 50t/hm2 of biochar applied for two consecutive years. The research result can provide a theoretical basis for the application of biochar in the black soil region.