This study aims at, the first, looking into existed approaches for syntactic binary parameter, the second, clarifying many problems awaiting solution, the third, suggesting alternatives. The chapter 1 clarifies the characteristics of parameter. The principles of universal grammar should be restricted ultimately as possible as it can and preserve the binary system of parameter settings which are manifested to only one of two constituents which are composed of parameter setting in order to help the children to acquire specific language in a short time. The concept of binary parameter setting be closely connected with universal principle of illusion. It also implies the one constituent is marked and the others unmarked. The chapter 2 digs up the approaches of parameter. The view of parameter divided largely into two. The one is binary parameter’s one and multi parameter’s one. The chapter 3 analyzes various language phenomena which seems to have multi attributes outwardly. The chapter 3.1 analyzes various language phenomena related to syntactic head direction. This chapter make clear the concept of binary system are unrepealed only if we understand the parameter are divided to two, parameter participating in “language to language” parameter and only participating inter language phenomena. The latter has property of time variance which triggers complementary relationship maintaining binary system. 3.2 analyzes various language phenomena related to syntactic PRO. This chapter make also clear the concept of binary system are unrepealed if we introduces universal principle of illusion, time variance acceptability, the parameter in conceptual intention system, and complementary relationship. (Daegu Univ.)