The purpose of this study was to investigate the validity on keyword matching scoring methods. In keyword extraction results, vocabulary differed according to a variety of writing performance of group classified from holistic rating results by human raters. Such are suggested that keyword matching scoring methods are valid to distinction of writing performance. As a result, high-level group keywords are deeper insight of topic and used to various ways of development in discussion. They also mainly used to vocabulary indicated the causal nexus in organization, formal and non-biased vocabulary in word selection. On the other side, low-level group keywords are mainly used to enumerate bits of examples way of development in discussion, emotional vocabulary which disrupt objectivity in the text. In addition, they are used to writer-centrism vocabulary which have colloquial, informal, biased traits. These result indicated that extract distinguished keywords between high-level and low-level group. Therefore, keyword scoring methods have validity in writing assessment system.