Muscle fatigue is one of the serious problems of functional electrical stimulation (FES), because possible standing time is limited by the fatigue. In this study, the three factors of muscle fatigue on FES standing in paraplegia is discussed. First, standing postures with a long leg brace (LLB) and two FES channels were analyzed. The subject was a male, 18-year-old, paraplegic patient with a T8 spinal cord injury. The knee joint flexion moment was calculated from the relationship between the zero moment point of the ground reaction force and the knee joint position. The estimated knee joint flexion moments were 16 Nm (FES) and 28 Nm (LLB). The average moment of three normal subjects was 14 Nm in the extending direction. It was found that the knee joint moment of a paraplegic is significantly greater than that of a normal subject. Knee flexion moment requires a large contraction force of quadriceps. This is one of the reasons for quadriceps fatigue. Second, the properties of muscle fatigue against electrical stimulation in paraplegia and normal subjects were measured. The contractile force decrease by 30 seconds' maximal intensity continuous stimulation varied from 44 to 10 percent in paraplegia. The contractile force decrease in normal subjects was 17 percent on average. The obvious difference between paraplegiacs and normal subjects was not found in the fatigue property. The high-intensity continuous stimulation is a serious problem, because it brings considerable muscle fatigue in both paraplegic and normal subjects. Finally, the fatigue rates caused by the 30 seconds' continuous stimulation and the 60 seconds' alternative stimulation, 3 sec on and 3 sec off, were compared. The alternative stimulation showed a lower fatigue rate. This result shows that stimulation stop or decrease can decrease muscle fatigue. According to this result, an FES standing device was developed. The device was used in the artificial reflex method, one of the stimulation sequences driven by knee joint flexion. In conclusion, three factors were pointed out. 1) Two-channel FES standing requires large quadriceps contractile force. 2) High-intensity continuous stimulation brings serious muscle fatigue. 3) Alternative stimulation decreases the muscle fatigue.