The invention relates to a mesoporous 4A zeolum and a preparation method thereof, belonging to the preparation fields of inorganic materials and ion exchangers, in particular to a mesoporous 4A zeolum containing 3-8nm mesopores in zeolum crystal particles and a preparation method thereof, wherein the mesopores can boost the cation exchange speed of the zeolum. The preparation method comprises the following steps: firstly, carrying out surface silanization on nano silica with organic silane coupling agent; taking the nano silica subjected to the surface silanization as a silicon source; adding sodium aluminate, sodium hydroxide and deionized water; and carrying out crystallization synthesis on the mixture under the hydrothermal condition. The porosity of the mesopores in the zeolum crystal can be regulated through changing the burdening ratio of the organic silane coupling agent to the silica. The mesopores can effectively shorten the diffusion paths of diffused molecules or ions in the micropores of the zeolum and reduce the diffusion resistance, thereby accelerating the exchange speed of cations especially larger hydrated cations and sodions in the zeolum. The preparation method is simple and is easy to control.