The pair annihilation effects on the Karpman-Washimi magnetization in quantum electron-positron pair plasmas are investigated in this paper. It is shown that the pair annihilation effect suppresses the ponderomotive magnetization and cyclotron frequency. It is also shown that the ponderomotive magnetization increases with an increase in the ratio of positron density to electron density if the pair annihilation probability is less than 50%. However, it is found that the ponderomotive magnetization decreases with increasing density ratio if the annihilation probability is more than 50%. It is also shown that the pair annihilation effect become more significant with increasing density ratio.