Abstract: The changes of soil organic carbon（SOC）,total nitrogen（TN）,microbial biomass carbon（SMBC）,microbial biomass nitrogen（SMBN） and enzyme activity index in different soil layers（0-20 cm in the surface layer, 20-40 cm in the middle layer, and 40-60 cm in the bottom layer） were studied by using the method of natural grass growing in the orchard with the wild grass species in the apricot orchard as the test material, in order to provide reference for exploring the influence of natural grass on the physical and chemical properties of soil in the apricot orchard in northwest Hebei.The results showed that natural grass significantly increased the contents of SOC,TN,SMBC and SMBN in soil layers of apricot orchard, and also increased the activities of catalase, sucrase, urease, cellulase and alkaline phosphatase in soil.With the increase of grass-growing years, the values of various indicators continue to rise.The indicators in the same soil layer were natural grass 8a＞natural grass 5a＞clear tillage（CK）,and the difference between the three was significant.With the increase of soil depth, the index values were as follows, surface layer＞middle layer＞bottom layer.The comprehensive grass growing years and soil depth, especially the 8-year treatment of natural grass in 0-20 cm soil layer, had the greatest impact.The contents of SOC,TN,SMBC and SMBN had increased by 62.48%,24.14%,130.33% and 76.96% respectively compared with clear tillage（CK）,and the values of qMBC and qMBN have significantly increased by 41.86% and 42.67% respectively compared with clear tillage（CK）.The activities of urease, cellulase and alkaline phosphatase were significantly higher than those of clear tillage（CK） by 81.82%,82.60%,257.30%,123.91% and 134.55%,respectively.Correlation analysis showed that there was a very significant correlation between microbial biomass carbon and nitrogen and organic carbon, total nitrogen and soil enzymes.It could be seen that long-term natural grass growth between rows in apricot orchard was an effective way to improve soil microbial biomass and soil enzymes, and played a key role in enriching soil fertility.