The design of a magnetic system for detecting the NMR spectra in a zero magnetic field for objects with the short times of spin-lattice relaxation T₁ > 10^-3 s is described. Two-stage switching of the magnetic field is used for effective excitation of magnetization evolution. The system consists of two magnetic coils. The first one produces the polarizing field of 0.12 T and the second one - the intermediate field in the range of 0 - 0.005 T. The circuit for coil current control and the procedure for choice of optimal conditions for spectra detection are described.