A descriptor is constructed to predict the composition of ABO3 perovskites that do not contain transition metals and have a high level of ionic conductivity (s). The descriptor consists of two parts: the ratio of ionic radii, RA/RB and the ratio of ionization potentials, VB/VA for A- and B- cations. Parameters for 100 perovskite compounds were considered to find the correlation dependences between the descriptor and the magnitude of s. Correlation selection approach is proposed to reveal a suitable correlation series. This approach allows determining the composition of perovskites that has a desirable ionic conductivity.