A real-time α/γ pulse shape discriminator based on CsI(Tl) scintillators is developed. The charge comparison method is adopted as an inserted algorithm. In this paper, the design scheme of the system is introduced and the real-time system is tested with a 60Co-γ source and a 241Am-α source. The influence of parameter setting on the discrimination result is investigated and the best parameter setting is provided. The results show that the designed real-time system has a small size. The best figure of merits is above 1.4. The system can discriminate α/γ events exactly and its counting rate of events can achieve 3×105 per second.