Nowadays, the barrier-free device in the human-computer interaction system is generally extremely expensive and its volume is large, which fail to really walk into the daily lives of people with disabilities. To develop a set of low cost, high precision, portable barrier-free character input system, this study designs a set of character input system based on EOG (Electro-OculoGram), puts forward a flashing character interaction based on regional optimization, and optimizes the dynamic threshold algorithm for identifying target character algorithm. Experiments showed that the system has realized the identification accuracy of 97.73%, nearly 100%, using equipment which costs less than RMB1000, and average character input rate of 1.95 characters/min.