This paper contrasts positional preposition zai (在) phrases in oracle bone inscriptions, bronze inscriptions and the Book of History (《今文尚书》). According to the relative positions of zai(在)phrases and the predicate central verbs, there are three structures: zai(在)+O +VP, VP+ zai(在) + O and zai(在) +O +NP. It is found that the grammatical functions and positions of the zai(在) phrases are same by comparing the objects of zai(在) with the modifying and supplemental components of their predicate center words and attributive center words, but their objects are most specific in the oracle bones inscriptions, and the semantic meanings of most central verbs of the predicate have their own characteristics, accordingly we could see the inheritance and development of the structures of positional preposition zai (在) in ancient Chinese.