Abstract: Arable land resources constitute the foundation of food security and sustainable development. However, with increasing pressures from economic development and land exploitation, the loss of arable land has become increasingly prominent. Policies play a crucial role in safeguarding the quantity, quality, and ecological functions of arable land. Taking Hainan Province as a case study, this paper examines the relationship between arable land protection policies and arable land loss, and reveals the mutual feedback mechanism between policy evolution and the effectiveness of arable land protection, providing a theoretical reference for government policy optimization. This study first analyzes the arable land protection policy documents issued by the central government and Hainan Province from 2000 to 2023 by constructing a PMGTS policy quantification model. An autoregressive distributed lag model (ARDL) is then employed to explore the dynamic relationship between policy characteristics and arable land conditions across different stages during the study period. The results show that: 1) the current policy system is characterized by strong resource input and relatively weak institutional effectiveness; 2) the evolution of the total policy effectiveness of arable land protection (TFE) exhibits clear stage transition characteristics, including four stages of exploration, adjustment, development, and optimization; 3) a negative correlation exists between arable land loss and policy adjustments. In the long run, improvements in policy effectiveness significantly restrain arable land loss, while in the short run the inhibitory effect shows a time lag; 4) the influence of policy effectiveness on arable land loss demonstrates an evident stage-specific strengthening pattern, and the coordinated transformation of policy mechanisms constitutes a key pathway for alleviating arable land loss. The findings indicate that a significant mutual feedback mechanism exists between the effectiveness of arable land protection policies and arable land loss in Hainan Province. Effective policy design therefore requires long-term planning and sustained policy support to enhance the effectiveness of arable land governance.