Abstract Grammatical errors are deviations that occur due to a lack of understanding from students about language rules. the aim of this study was to find out the most dominant type of grammatical errors in writing procedure text made by the tenth grade students at man 3 palembang. the study used quantitative method. the participants of this study was one class of tenth grade students selected in using purposeful sampling technique. the data obtained from writing test were analyzed by using percentage as a procedure of data analysis. the results of this study indicated that four types errors were made by the students. they covered 34 (24,46%) errors in addition, 37 (26,62%) errors in omission type, 53 (38,13%) errors in misformation type and 15 (10,79%) errors in misordering type. meanwhile, the most dominant type of error was misformation type amountly to 53 (38,13%). Key words: error analysis, grammatical error, procedure text,