Students have variaty personalities. Personality is considered as one of the individual differences which is greatly agreed to have an influence on learning in general and second language acquisition (SLA) in particular. The first objective of the research was to explaine how is students’ personality at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/2018. The second objective of the research was to explaine how is students’ ability in writing informational report at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/2018. The third objective of the research was to explaine is there any influence of introvert personality to students’ ability in writing informational report at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/2018. This research is quantitative research. The researcher used questionnare, test, interview and documentation. The result of this study shows that there is not influence of introvert personality to students’ ability in writing informational report at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/2018. The result of this study shows that the introvert students’ personality at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/ 2018 is medium category, it is 7.13 on interval 6.18 – 8.08. Meanwhile, The students’ ability in writing informational report at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/ 2018 is medium category, it is 69.12 on interval 58.795-79.465. The influence of introvert personality to students’ ability in writing informational report at the eleventh grader of MA Fathul Ulum Grobogan in academic year of 2017/2018 is 1.102093513. It means the influence of introvert personality to students’ ability in writing informational report is not significant.