We report on an abnormal migration phenomenon of alkali ions in calcium silicate glasses, induced by 250kHz, 800nm femtosecond laser irradiation. The diameter of the laser-affected zone is not dependent on the glass-transition temperature of glass samples. Elemental analysis by Electro-Probe Microanalyzer demonstrates that K ions migrate to the periphery of the laser-affected zone, while Cs ions show an opposite tendency in the two alkali ions coexisting glass. The possible mechanism on the observed abnormal phenomenon is discussed.