[Objective] The effects of wood-source biochar on the soil aggregate structure were studied to find a suitable biochar addition and to provide a scientific basis for improving the soil structure and increasing crop yield for solar greenhouse soil in Yangling District, Shaanxi Province.[Methods] Five biochar treatments of 10, 30, 50, 70 and 90 t/hm², and a control treatment without any biochar, were set up. For all treatments, soil aggregate mean weight diameter, geometric mean diameter, damage rate and fractal dimension were calculated through the dry sieve method and the wet sieve method. And, crop yields under different biochar additions were also analyzed. Finally, an appropriate biochar addition was concluded both in considering soil aggregates and crop yields.[Results] The results showed that the mechanically stable dry aggregates significantly increased by 0.6~4.6 mg/kg and the dry microaggregates decreased by 4.0%~32.6% compared with that of control treatment. Further, after adding biochar, 3~2 mm, 2~1 mm and 1~0.5 mm water stable large aggregates increased by 25.3%~41.2%, 22.7%~74.2%, 9.1%~46.4% respectively; however 0.5~0.25 mm water stable large aggregates decreased by 2.1%~18.1%. Biochar could promote the formation of small size microaggregates, but have a non-significant effect on microaggregate stability and microaggregates. Additionally, biochar had a positive effect on the spinach fresh weight with an increase of 68.8%~214.9%.[Conclusion] Biochar can ameliorate the soil aggregate structure. Taking soil aggregates and crop fields into account, the 70 t/hm² biochar has the optimal effect in greenhouse.