In prevailing optical metalens design, phase-shifting elements are primarily realized through physical mechanisms, such as resonant scattering and orientation-dependent phase retardations. This study introduces a novel approach to control the phase-designing elements. We establish a topologically protected complete $21\pi$-phase variation encircling an exceptional point in the Si-dielectric metalens, which can be conceptualized as a non-Hermitian system. More specifically, the Si-dielectric metalens comprises S-shaped cuboidal structural units, and the required phases are obtained by modifying the geometrical parameters of these units. The metalens exhibits superior focusing performance at a center wavelength of 570 nm, with a bandwidth of 70 nm, along with a satisfactory field of view and efficiency. Our findings pave the way for novel mechanisms and the design of functional photonic devices for wave manipulation, futher integrating exceptional point physics with flatland optics.