This study is a multicenter, randomized, double-blind, double-dummy, active- and placebo-controlled, parallel-group clinical trial. The dose confirmation stage is designed to evaluate the efficacy and safety of different doses of huperzine A controlled-release tablets in patients with mild-to-moderate dementia of the Alzheimer's type, with the goal of providing a basis for dose selection in the subsequent efficacy confirmation stage. The efficacy confirmation stage aims to assess the effect of huperzine A controlled-release tablets on cognitive function and functional abilities in patients with mild-to-moderate dementia of the Alzheimer's type.In the open-label extension stage, all subjects will receive huperzine A controlled-release tablets until Week 52, to further evaluate the long-term efficacy and safety of the treatment.