A closed-loop heat pump drying system based on air heat recuperation was designed to enhance drying performance. To optimize system efficiency, adjustable parameters during the drying process were investigated. Multiple experiments were conducted to analyze the effects of bypass ratio, drying chamber temperature, and circulating airflow velocity on the recuperation system, and performance comparisons were made with a non-recuperative system. The experimental results indicate that each of these three factors, including bypass ratio, drying chamber temperature, and circulating airflow velocity, has an optimal value. The recuperation system improved the specific moisture extraction rate (SMER) by 5.57%~37.40%, depending on the conditions. Compare with the non-recuperative system, the optimized recuperation system achieve an SMER enhancement of 7.71%~22.78%.