In this paper,we have obtained LIF spectrum of D1 ∏→ X1 ∑+ of NaK induced by 514. 5 um of CW Al+ laser, assigned the spectrum by the known molecular constants, analysed and discussed the emission mechanism of LIF in detail. The vibrational constants of X 1 ∑+ state have been provided by using the least-square fit. The calculated wavelength values are in good agreement with the measured results. We also calculateFranck- Condon factors and intensities of each Q-branch transition. The computed intensities coincide with the observed very well in considering dependence of transition dipole moment Re(r) on r. It proves that the values of vibrational and rotational quantum numbers (v,J) we have determined are reasonable.