With the development of small satellites, planar array has become a promising configuration in the very low frequency (VLF: 3–30 kHz) space-borne transmitting system in the near future. In this manuscript, a theory towards a VLF planar array immersed in magnetized plasmas is proposed, which contains both closed-form expressions and numerical techniques. The kernel function for the planar array is derived from the analytical expression of the field radiated by a point current source, and the integral equation is set up based on the boundary condition. By introducing the ten-term form of current distribution and the digital filter of fast Hankel transformation, the matrix of the integral equation is solved with considerable accuracy to determine the current distribution and fed-point impedance under various parameters. With the help of the induced EMF method, the mutual coupling impedance is also determined and discussed. The correctness and the accuracy of the proposed method are shown by comparing the computed result with earlier work and the simulated result by EM simulation software CST Studio Suite.