This paper explores the Chinese Buddhist translation of “suo-yi zhe he” (所以者何) from three aspects. First, there are two Sanskrit counterparts, “tat kasya hetoḥ” and “tat kasmāt hetoḥ” from the Indian source. From Pāṇini’s grammatical perspective, “hetoḥ” in the former is parsed as genitive. From the Pāli tradition, however, it is considered ablative. Secondly, I study the Chinese translation’s origin, syntactic as well as semantic structures based on commentaries in the Tang Dynasty. There are two possibilities, one is from the structure “suo” (所), the other being a simple subject-predicate one. As I traced back to its origin, I found that it is also likely an abbreviation of “suo-yi ran zhe he” (所以然者何), without excluding the possibility of colloquialism in its time. Finally, I try to compare “suo-yi zhe he”(所以者何) with its Indian parallel and go into three comparative analyses based on the three possibilities.