【Objective】Content of calcium carbonate and equivalents and pH are two important properties of the soil, which will affect availabilities of soil elements and nutrients, and consequently soil fertility and quality. It was demonstrated in previous studies that content of CaCO₃ and equivalents did affect soil pH and some other soil properties. Generally speaking, with increasing content of CaCO₃ and equivalents, soil pH gradually rises and levels off in the end. What’s more, their relationship could be described with an inverse function model. This study was carried out in the Heihe River Valley, which is the second largest inland river valley and a typical one, located in the western part of the Hexi Corridor in the arid region of Northwest China. In this area, the relationship between soil pH and content of CaCO₃ and equivalents may vary and was therefore analyzed from the aspects of region, altitude, soil parent material, soil type and land use. 【Method】Based on the data gathered during the 2012—2013 soil survey of the valley, correlation analysis and regression analysis were performed of variation of soil pH with content of content of CaCO₃ and equivalents. 【Result】Results show that soil pH had a significant nonlinear relation with content of CaCO₃ and equivalents as previous studies disclosed, i.e., soil pH gradually rises with the increasing content of the substance, declined in its rising rate when the content reached a certain level, and leveled off in the end. However, the relationship between the two varied in degree with region, altitude, soil parent material, soil type and land. Specifically, soil pH was significantly and positively related to content of CaCO₃ and equivalents in the valley as a whole and in the upstreams of the river, and in anthrosols, halosols, isohumosols and cambisols, regardless of elevation and land use. However, no significant relationship was found in soils derived from aeolian, diluvial and alluvial deposits. In addition, the optimal regression model for analysis of relationship between the two varied with the region, altitude, soil parent material, soil type and land use, and may be a power function model, a quadratic model, a cubic model or a linear model, instead of a simple inverse function model as obtained in previous studies.【Conclusion】The relationship between soil pH and content of CaCO₃ and equivalents in the Heihe River Valley is complex, which may be related to its vast spatial span, great altitude gradient, different soil forming factors and diversified soil types.