A model of magnetically confined discharge carbon monoxide laser is presented in this paper.Electron energy distribution function and the influence of the magnetic field on electron impact excitation rates are discussed.The vibrational-state populations of CO molecules and small-signal gain with magnetic field are calculated.The electron density in the energy region corresponding to the maximum electron impact exitation cross sections of CO molecules increases greatly due to magnetic field being added.The electron impact excitation rates,the vibrational-state populations and the laser small-signal gain increase.