A new experiment to test lepton flavor universality by measuring R K=Γ(K +→e +v)/Γ(K +→μ +v) ratio with an accuracy of ΔR K/R K = = 0.2 has been proposed. The SM prediction of R SMk is known with excellent accuracy, and a possible mechanism to detect the LFV SUSY effect through a deviation from the μ-e universality has been discussed. The experiment will be performed at J-PARC employing a stopped K + beam in conjunction with a 12-sector iron-core superconducting toroidal spectrometer and a CsI(Tl) calorimeter. The R K value can be obtained from the number of the accepted K +→e +v and K +→μ +v events corrected for the detector acceptance. The experimental sensitivity is estimated to be ΔR K/R K=0.2. © 2012 American Institute of Physics.