A laminated passivation structure of solar cell and a preparation method thereof are disclosed herein. The laminated passivation structure of solar cell includes a P-type silicon substrate, a first dielectric layer, a second dielectric layer, a third dielectric layer and a fourth dielectric layer sequentially arranged on the back surface of the P-type silicon substrate from inside to outside. The preparation method includes generating a first dielectric layer on the back surface of the P-type silicon substrate, and then sequentially depositing a second dielectric layer, a third dielectric layer and a fourth dielectric layer on the first dielectric layer.