This paper is intended to show how the differences of aspects of phonological development between literary reading and colloquial reading in Old Mandarin can be explained in a unified manner under Optimality Theory. Because the differences of aspects of phonological development between literary reading and colloquial reading in Old Mandarin is a complicated phenomenon, in the previous researches, it has been focused to reveal order of phonological rules between literary reading and colloquial reading in Old Mandarin. Therefore, in this study I attempt to account for the differences of aspects of phonological development between literary reading and colloquial reading in Old Mandarin with new constraints and ranking on the basis of diachronic phonological changes.