The type II codes have been studied widely in applications since their appearance. With analysis of the algebraic structure of finite field of order 4 (i.e., GF(4)), some necessary and sufficient conditions that a generalized H-code (i.e., GH-code) is a type II code over GF(4) are given in this article, and an efficient and simple method to generate type II codes from GH-codes over GF(4) is shown. The conclusions further extend the coding theory of type II.