The magnetic field gradient induced transverse relaxation rate of noble gas atom spins has an important role on the sensitivity of the Nuclear Magnetic Resonance Gyroscope. In order to improve the gyro sensitivity, the magnetic field gradient needs to be suppressed. In addition to the environmental magnetic field gradient, the equivalent magnetic field gradient caused by the polarization inhomogeneity of Rb atoms also exists in the cell of the gyro sensor head. Therefore, a main magnetic field homogenization method based on gradient compensation coil and double beam reverse compensation is proposed. A multi field coupling dynamic model including Rb electron spin polarization, nuclear spin polarization and pumping light field propagation is established. The quantitative relationship between the magnetic field gradient of the cubic cell and the relaxation of Xe nuclear spin is obtained by the finite element analysis method. Through experiments and numerical analysis, the equivalent magnetic field homogenization method by the gradient coil and the reverse propagation double beam uniform pumping is studied. The experimental and numerical results show that T2 of 129 Xe is improved from 3. 6s to 5. 7s in a 5X5X5mm3 cell and the polarization uniformity of Rb atom has been significantly improved in both longitudinal and transverse directions. The equivalent magnetic field of 1st order has been significantly suppressed, and the lateral spin relaxation rate of Xe nucleus caused by the residual second-order equivalent magnetic field gradient has been reduced to about 10-4 . s-1.