Excessive grounding current on metal sheath of single-core high-voltage cable will bring massive additional loss to the cable, which reduces the cable′s current-carrying capacity and safe operation lifetime. In order to analyze the grounding current in metal sheath, a mathematical model of grounding current calculation and relevant program are established aiming at single-core high-voltage cables in cross-bonding grounding mode. The calculation results prove that the program is competent to reflect actual grounding current. Furthermore, the relationship between grounding current and its influencing factors such as grounding resistance, sheath parameters and earth resistivity is analyzed. The results of analysis indicate that the grounding resistance has a great influence on the grounding current, while in actual engineering the parameters of metal sheath do not. Grounding current is sensitive to earth resistivity only when the value of earth resistivity is low. The research conclusions provide a theoretical basis for the operation and maintenance of high-voltage cables.