This study aims to determine the analysis of student's critical thinking ability based on gender in the arithmetic sequence and series material at MTs Negeri 1 Palembang. This study's type is a qualitative descriptive study. This study was performed with a population of seven classes and a sample of one class, namely class VIII D, in the odd semester of the 2018/2019 academic year. Data collection techniques used documentation, tests, and interviews. At the same time, the test data analysis technique used descriptive narrative. Based on the research results, the results obtained: 1) Female students have higher critical thinking ability than male students in arithmetic sequence and series material. This is because female students have more complex thoughts than male students. 2) Male students are slightly superior by 10% over female students in achieving conclusions. 3) Male and female students have the same ability in indicators to make further explanations.