The magnetic particle imaging (MPI) is a new dynamic targeting imaging method in the human body. However, the current MPI system mainly utilizes a closed magnetic field scanning structure, which severely limits its clinical application. In this article, an open electrical scanning narrowband MPI system is designed. On the basis of analyzing the harmonic magnetization response of superparamagnetic particles, an open spatial positioning magnetic field based on field free line is formed by using eight gradient coils through the calculation of the coupling magnetic field on the coil surface and the current control. The imaging area is 30 mm×30 mm. A single side excitation coil is used to generate a 20. 7 kHz excitation magnetic field. The superparamagnetic nanoparticles tracer in the high-frequency excitation magnetic field and the positioning magnetic field generates a locatable superparamagnetic magnetization signal with rich harmonic components. A high signal to noise ratio Gradiometer coil is used to detect its third harmonic signal to form a voltage cloud image. Furthermore, the non-negative least square method is used to reconstruct the voltage nephogram through the pre-measured system function matrix to form the tracer concentration distribution nephogram. The imaging experiment results show that the detection sensitivity of the system in the open imaging area is 20 μg Fe, the spatial resolution of image reconstruction is 2 mm, and the imaging speed is 1 fps. The good open imaging effectiveness is achieved. This system is also the first open magnetic particle imaging system independently developed in China.