Abstract: In Cd-contaminated agricultural soils, straw incorporation promotes resource recycling but may also increase the risk of Cd remobilization. However, the interactive effects of long-term silicon (Si) fertilization and straw management on soil Cd stabilization and Cd accumulation in rice remain unclear. To investigate the effects of continuous Si application combined with straw incorporation or removal on Cd migration and accumulation in the soil–rice system, a three-year field experiment was conducted in Yong'an Town, Liuyang City, Hunan Province, China. Four treatments were established: Si application with straw incorporation (+SiR), Si application with straw removal (+SiNR), no Si application with straw incorporation (−SiR), and no Si application with straw removal (−SiNR). The results showed that both Si application and straw management significantly affected Cd accumulation in rice, and their interaction became increasingly pronounced with prolonged treatment duration. Continuous Si application significantly increased soil available Si concentration and soil pH, promoted the transformation of Cd into Fe-Mn oxide-bound and residual fractions, and thereby reduced Cd bioavailability. Compared with the −SiR treatment, continuous Si application significantly decreased the available Cd concentration in soil and Cd concentration in brown rice, with the greatest reductions observed in the +SiNR treatment, reaching 36.67% and 55.56%, respectively. Although the +SiR treatment resulted in the highest soil available Si concentration, Cd re-input during straw decomposition may partially offset the Cd immobilization effect of Si application. Correlation analysis showed that soil available Cd was significantly negatively correlated with soil pH (r = −0.89, P < 0.001) and straw Si concentration (r = −0.60, P < 0.05). Rice Si accumulation was negatively correlated with Cd concentration, indicating that enhanced Si accumulation may help reduce Cd translocation from roots to shoots and grains. These findings provide a theoretical basis for optimizing straw management and the rational application of Si fertilization in Cd-contaminated double-cropping rice fields.