To meet the continuous mining demands of open-pit coal mines, this paper systematically studies the design theory and synchronous control technology of sandwich belt conveyors. Through theoretical derivation and experimental validation, conveying capacity and pressing force models are established, revealing that syn-chronous operation of the dual belts reduces pressing force by approximately 50%. A stress-superposition-based method for calculating concave/convex arc radii and a simplified design approach for multi-layer belts are proposed. A dual-belt synchronous control system based on PID and cross-coupling compensation is developed, integrating a speed-tension cooperative protection mechanism to achieve high-precision dynamic matching and anti-slip protection. Verification using a prototype with a 1200 mm belt width and a 60° inclination demonstrates the accuracy of the theoretical models and the effectiveness of the synchronous control. The research provides key technical support for the domestic application of sandwich belt conveyors.