The purpose of this study is to examine the changes in grammar research in North Korea before and after the establishment of the Cultural Language Grammar, focusing on the works of Su-Kyung Kim. The paper is organized as follows. First, Su-Kyung Kim formed the basis of North Korean grammar through his research on language norms, parts of speech, and morphology. He sought to relate theoretical research to language norms. The issue of diphthongization of Chinese character sounds was a problem that was linked to the language policy of abolishing Chinese characters and using only Hangul, and he sought to link theoretical research to practical use. Next, he prepared the criteria for part of speech and led the discussion on the part of speech of 'to(토)'. By establishing the criteria for 'to', it was possible to differentiate morphology from part of speech theory. Second, in the 1970s, based on previous grammar research, 'part of speech' was separated from morphology and word composition was emphasized. By the 1980s, grammar systems consisted of ‘part of speech, morphology, sentence structure, and word formation’. Third, the impact of Kim's grammatical research on North Korean grammar research is that he first emphasized the importance of matching 'to' and sentence components as an important principle of grammatical description. Next, he introduced the 'form-oriented functional grammar' approach to grammar and emphasized the linguistic characteristics of Korean language by setting up the symbolic history in the grammar system. Finally, by identifying the grammatical characteristics of ‘to’, it formed a framework for later classifying ‘to’ in part of speech and describing it in morphology. Kim came up with a linguistic theory that was in line with the language policy of a socialist country and made it possible to realize it practically. He studied the advanced theories of Western linguistics and philology to develop a grammar with systematic coherence by matching morphology and sentence components.