Ergonomics evaluation of forest-fruit-picking machine is very important to design harvest machinery. In order to study the ergonomic features of knapsack forest-fruit-picking machine, a fatigue evaluation model of upper limb biceps brachii muscle based on surface electromyography (sEMG) signals was established by arm fatigue test. Combining the heart rate test and the model, the arm fatigue characteristics of the knapsack forest-fruit-picking machine and handheld picking machine were compared. The results showed that increasing ratio of heart rate and fatigue degree with knapsack forest- fruit-picking machine were less than those with handheld picking machine in the same situation. Therefore, the knapsack forest-fruit-picking machine is more labor-saving than the handheld picking machine, and can effectively relieve muscle fatigue.