In order to estimate the harmonic current injected into the nodes and locate the harmonic source effectively when the system is not globally observable, a harmonic source location method based on orthogonal matching pursuit algorithm is proposed in this paper. Based on the known measurements and measurement matrices and the orthogonal matching pursuit algorithm in the compressed sensing theory, the undetermined system harmonic state equation is solved, and the harmonic current injected into the nodes is estimated, so that the harmonic source can be effectively located when the system is not globally observable. Through simulation and comparison with other methods, it is verified that the proposed method has better positioning effect when changing the number and position of harmonic sources and considering measurement errors. It shows that the proposed method has higher applicability and anti-interference ability.