In this paper, the notion of transformational programming language is introduced. The new language constructs-"transformation module" and "transformation control directive" are defined. They play the key roles in the transformational programming languages. We explain that a transformation module can be used to describe a partial implementation of an abstract data type and a transformation control directive can be used to apply a transform defined by a transformation module to an abstract variable and the related operators in a program.Some of the important issues,such as abstraction,expressiveness and flexibility of reprentation in the transformational programming language and correctness of the rtansformational program are discussed in the later part of this paper.