Due to the high economic benefits of orchard，the conversion of farmland to orchard is widely promoted in Guanzhong plain.In order to explore the difference of soil organic carbon component content and soil carbon pool index after farmland was transformed into orchard in Guanzhong plain，field investigation and indoor analysis were used to explore the change of soil organic carbon(SOC)component and soil carbon pool management index in orchard and farmland ecosystem in Guanzhong Plain.The results showed that in 0～20，20～60 and 60～100 cm soil layers，the content of soil active organic carbon(LOC)in orchard increased by 33.91%，49.95% and 35.37% compared with that in farmland，respectively.Compared with farmland，orchard significantly increased LOC/SOC value in 20～60 and 60～100 cm soil layers，improved the activity of deep soil carbon pool，and promoted the utilization of soil organic carbon.LOC content of orchard and farmland decreased with the increasing soil depth in 0～100 cm vertical gradient，while SOC content had no significant difference.The carbon pool index(CPI)and carbon pool management index(CPMI)of orchards were 6.12% and 72.72% higher than those of cropland，respectively.The correlation analysis showed that SOC，LOC，non-active organic carbon，carbon pool activity and CPMI were closely related to the main soil fertility factors，and could be used as the main monitoring factors of soil fertility in farmland ecosystem in this region.The results show that the change of land use pattern from farmland to orchard in Guanzhong plain will effectively activate the inherent carbon pool in deep soil，promote the decomposition and utilization of organic carbon，and promote the benign development of soil properties.