This Research is aimed to test the effectiveness of game-based learning multimedia in order to improve student learning outcomes on English subject with the tpic of grammar in the classroom. The research development of multimedia game-based learning using the procedure of Raiser and Demsey consisting of 8 stages namely:1) Analysis, 2) Design 3) Development. 4) Implement, 5) Evaluate. The trial of product development tested had passed several processes covering; the review from media’s expert which includes software changes and visual communication, the review from content’s expert covers material and instructional design, students’ responses towards products’ usage and attractiveness, small group and big group test trial. The results of the feasibility test of a team of experts covering media expert results obtained 4,7 categorized as very good and content experts 4,7 which is at a range of very good category. After the product is revised based on the experts’ input, it is tried and tested to the trial class students at a small group scope with the result of 4,6 for their responses to the product and improving score from the pretest which is 52,11 to be 67,55. Next, at the large scale trial at the experiment class to see the effectiveness of the game based learning multimedia shows that there is a difference on the student’s learning result.  On the pretest of control class, the score is 56.00 and the final score in the posttest of the same class is 64,43.if it is compared with the pretest score from the experiment class, the score is lower which is 55.90, but it improves rapidly on the posttest after being treated with multimedia game based learning and come to score 71.65 with the significant value 0.05. thus, it can be said that the result of the development of multimedia game-based learning is effective to improve students learning outcomes.