This research is aimed at revealing: (1) whether and to what extent Johnny Grammar’s Word Challenge activities through STAD can enhance students’ grammar  in  writing,  (2)  and  explaining  the  class  situation  when  Johnny Grammar’s  Word  Challenge  activities  through  STAD  are  implemented  in teaching grammar in writing. The classroom action research was conducted in two cycles.   Each   cycle   consisted   of:   planning,   implementing,   observing,   and reflecting. There were two kinds of data, qualitative and quantitative. The qualitative data were collected through observation, interview, questionnaire and field note. The quantitative data were collected through the students’ pre-test and post-test. The qualitative data were analysed by using Interactive Model, while the quantitative data were analysed by using descriptive statistics.
The result of the research showed that Johnny Grammar’s Word Challenge activities through STAD could enhance the students’ grammar in writing and class situation. Through Johnny Grammar Word’s Challenge activities through STAD, the students showed their improvement in grammatical aspects in writing aspect, they are: verbal and nominal sentence, pronoun, modal, possession, adjective and adverb. Meanwhile the improvement of class situation was indicated from positive interaction among the teacher and students, mutual respect and contribution, peer collaboration, and classroom talk practiced by students.
In conclusion, implementing Johnny Grammar Word’s Challenge activities through STAD can enhance the students’ grammar in writing in descriptive text and class situation. In other words, this application gives benefit for students to achieve better result in grammar in writing and make them interested in grammar sin writing class.Therefore, Johnny Grammar’s Word Challenge can be an alternative method for the teacher or the future researchers who will conduct a similar research.