［Objective］ The soil erosion and quality under chestnut forests were quantitatively analyzed at earth-rocky mountainous area in northern China to provide a theoretical basis for studying， managing， and conserving the soil and water in economic forests in mountainous area with rocky soil in northern China. ［Methods］ Twelve soil parameters， such as soil erosion modulus， soil particle size distribution， organic matter， and total nitrogen， were measured for chestnut forests and the surrounding shrub forests in the Zhujiawan （Miyun District） and Badaohe （Huairou District） watersheds in Beijing City from 2022 to 2024. The soil fertility， soil coarsening degree， and erosion intensity were analyzed， and the soil quality index （SQI） was evaluated using principal component analysis. ［Results］ ① The annual average soil erosion modulus of the chestnut forest was 8.3 times higher than that of the shrub forest. The rill erosion modulus of the chestnut forest after flood season was more than 13 000 t /km2， and the understory erosion was intense from 2023 to 2024. ② The coarse sand （0.5—2 mm） content in the 1 cm soil of the surface was approximately 1.3 times higher on average in the chestnut forest than in the shrub forest， indicating the soil was coarser in the chestnut forest. ③ The average organic matter， total nitrogen， and alkali-hydrolyzed nitrogen contents in the soil of chestnut forest were less than one-quarter of those in the adjacent shrubland. The available potassium content in the chestnut forest soil was approximately half of that in the adjacent shrubland. The available phosphorus and low-availability potassium contents showed enrichment phenomenon in the chestnut forest soil. ④ The SQI of the chestnut forest was significantly lower than that of shrubland （p=0.025<0.05）. ［Conclusion］ The soil in chestnut forests at earth-rocky mountainous area in northern China was experiencing severe erosion， soil coarsening， and nutrient loss； the quality of this soil was lower than that of the soil in the surrounding shrub forests. Scientific land management measures need to be implemented to increase the quality of this soil.