Potassian vapor was irradiated in a glass fluorescence cell with pulses of radiation from a optic parametric oscillator (OPO) laser ,populatingK2(1Λg) state by two-photon absorption. Energy transfer in K2(1Λg)+K collision is studied by using molecular fluorescence. The K number density was determined by the optical absorption measurement. The decay signal of time-resolved fluorescence from 1Λg→11Σ+u transition was monitored. The effective lifetimes of the 1Λg state can be resolved. The plot of reciprocal of effective lifetimes of the 1Λg state against K densities yielded the slope that indicated the total cross section for deactivation and the intercept that provided the radiative lifetime of the state. The radiative lifetime 20±2 ns is obtained. The cross section for deactivation of the K2(1Λg)molecules by collisions with K is 2.5±0.3×10-14 cm 2. At the different K densities ,the time resolved and the time-integrated intensities of the resulting K23Λg→13Σ+u line were measured. The absolute values for K2(1Λg)+K→K2(3Λg) +K collisional transfer cross section has been obtained. The cross section is1.1±0.3×10-14 cm2.