Retroreflective article is different from other reflecting objects as it returns the incidence ray to the near of its source. This characteristic makes the retroreflectors have many applications in reflective highway signs, reflective vests, and other safety-relaxed items. These articles may have various shapes. However, the quantitative evaluation of performance for the best shape of retroreflector needs much time and cost for manufacturing prototypes and for performance experiments. In this work, we have developed a program for simulating the trace of ray entered into a retroreflective element, in order to determine the optimal shape of retro-reflection. We have also proposed new performance criterion of retroreflective articles, which can confide the range of incidence angle, instead of the criterion with the merely retroreflective strength.