The process of the e−e+ pair photoproduction in a strong magnetic field through the polarization cascade (the creation of an e−e+ pair from a single photon and its subsequent annihilation to a single photon) has been considered. The kinematics of the process is analyzed, and the expression for the general amplitude is obtained. A radiation correction to the process of pair creation at the lowest Landau levels by a single photon is found in the case where the energy of this photon is close to the threshold value. A comparison with the process of e−e+ pair production by one photon is made.