The vast Karst area in southwestern China is ecologically fragile region, where both soil organic carbon (SOC) and total nitrogen (TN) are evidently sensitive to LUCC. However, there has not been any comprehensive study to analyze the effects of LUCC on SOC/TN in this region based on large data ensembles. In this paper, the response of SOC and TN storage to LUCC (i.e., deforestation and land restoration) in the Karst region of southwestern China was investigated by meta-analysis, which was found to be controlled by a series of impact factors, such as the type of LUCC, sampling depth, calculation methods and environmental factors. Based on 471 sets of SOC data and 468 sets of TN data, Firstly, we evaluated the calculation methods (i.e., fixed-depth method, the main deviation from the two methods was that the FD procedure neglected the heterogeneity of soil bulk density, which may underestimate the loss of SOC and TN after deforestation but overestimate the benefits of land restoration to SOC and TN. Secondly, we found that when woodland and grassland were converted to cultivated land or other land types, SOC and TN losses were greater; while other LUCCs had less impact. Similarly, land restoration increased the SOC and TN, especially the restoration from farmland to forests. Also, we demonstrated that increasing the soil sampling depth could significantly alter the response of SOC and TN to LUCC. Finally, the environmental factors affecting SOC storage (such as soil properties, geographic and climatic factors and duration) were discussed.