At present, the mathematical model of three-phase imbalance degree based on sequence component is not unique, and the sequence component is not easy to measure in practice. This causes a lot of inconvenience to three-phase imbalance treatment and loss analysis due to three-phase load imbalance. Based on three kinds of three-phase load imbalance conditions, a corresponding three-phase load imbalance degree algorithm is proposed. For three-phase unbalanced load power systems with unbalanced amplitude and phase, the reciprocal of the square sum of the ratio of the effective value of the sequence component to the effective value of the three-phase average current is proposed to measure the three-phase load imbalance. The relationship between the three-phase sequence component and the three-phase load imbalance is established, and the three-phase imbalance measurement formula based on the sequence component proposed by IEC is unified. Experiments and case studies show that the proposed three-phase load imbalance algorithm can effectively reflect the imbalance under different conditions. For low-voltage power supply and distribution system, the proposed algorithm is consistent with the proposed three-phase load imbalance algorithm for three-phase power system with unbalanced amplitude and phase. This has strong practical value for the treatment of three-phase imbalance and engineering practice.