In processing computer display and printing, complex scripts exhibit very sophisticated language features. A complex scripts processing model based on predication rules is brought forward. The glyph layout features of complex scripts are formalized by predication rules. According to the process of complex scripts processing steps, the software system framework implementing this model is designed. By separating the language features of complex scripts from the programming control logic, the system flexibility is improved. Furthermore, it's convenient to add supports of new complex scripts. The development of office suite for Mongolian, Tibetan and Uighur languages has proven that this model is useful and effective.