The laser-inducea fluorescence (LIF) spectrum of Q-branch of C1∏u(v =0, J = 105)- X1∑g+(v"=1-10, J" = 105) for dimer 39K2 excited by 4415.6 A CW He-Cd laser was reported. The vibrational constants of X 1∑g+ and the Te value of C1∏u for 39K2 were obtained by last-square fitting. The spectrum analysis showed that the Te= 22968cm-1 of C1∏u for 39K2 was suitable. The Franck-Condon factors of the (v = 0, J = 105) - (v" = 1-10, J" = 105) transitions for dimer 39K2 were computed by using Morse potentials. The agreement between the computed intensities and the experimental ones was satisfactory. The analysis of r-centroid approximation showed that the changing ratio of the electronic dipole transition moment Be for dimer 39Ka was 0.157~0.168 detye/A(4.22 A