Late-model ionic clusters of KNO_3 were formed under the conditions of electrospray ionization. A series of peaks of the ionic clusters could be observed in the electrospray ionization mass spectra(ESIMS). The general formulae of the ionic clusters were deduced to be K~+(KNO_3)_n and NO~-_3(KNO_3)_m. By referring to the crystal structure of KNO_3, the possible configurations of these new typical ionic clusters were speculated based on the calculated data by means of the Gaussian-94~x computer program. Late-model ionic clusters of KNO 3 were formed under the conditions of electrospray ionization. A series of peaks of the ionic clusters could be observed in the electrospray ionization mass spectra (ESIMS). The general formula of the ionic clusters were deduced to be K ~ + (KNO_3) _n and NO ~ -_3 (KNO_3) _m. By referring to the crystal structure of KNO_3, the possible configurations of these new typical ionic clusters were speculated based on the calculated data by means of the Gaussian-94 ~ x computer program.