Spin exchange optical pumping is an efficient technique to obtain large quantities of hyperpolarized <sup>129</sup>Xe nuclei. The spin oscillating perturbation theory for spin exchange optical polarized <sup>129</sup>Xe nuclei is established in this paper. The theoretical framework relies on the perturbation method of the steady state solution to derive the rate equations and analytical solutions of <sup>129</sup>Xe nuclear spin. This model gives rise to a novel fast determination of longitudinal relaxation time <i>T<sub>1</sub> </i>for the hyperpolarized 129Xe nuclei. This direct measurement method is applied to the <sup>129</sup>Xe in the gas phase and reduces the time consuming than the conventional inversion-recovery method. The method exhibits potential role in the development of the samples with long longitudinal relaxation time.