There is a problem in that the existing harmonic current detection method does not consider the coupling phenomenon of the harmonic current at the common connection point. This leads to the unsatisfactory harmonic control effect. Thus this paper proposes a load harmonic current detection method to effectively solve the problem. Having analyzed the shortcomings of existing detection methods, this paper draws on the idea of decomposing current in the German DIN40110-2 standard, takes the harmonic voltage as the benchmark, and according to the principle that the active power consumption of the load before and after the equivalent is unchanged, the harmonic equivalent conductance, the lumped harmonic voltage and the lumped harmonic active power are defined. The Hilbert transform is used to shift the phase of the harmonic voltage. Then the lumped harmonic reactive power and harmonic equivalent susceptance are defined, and the harmonic current generated by the background harmonic voltage is decomposed. Accordingly, the load harmonic current can be detected, and compensation of the load harmonic current in the background harmonic voltage environment can be realized. Simulation analysis and measured data verification results show that the proposed method can effectively improve the harmonic control effect of the public connection point by compensating the detected harmonic current. This work is supported by the National Natural Science Foundation of China (No. 51777166).