The aims of the study is to know whether or not Semantic Mapping is effective in improving Student’s Reading Comprehension on The Second Grade of MTs Ma`arif NU12 Arenan, Purbalingga in Academic Year 2009/2010).The method used was quasi experiment. The population of this research was the second grade of MTs Ma`arif NU12 Arenan, Purbalingga in Academic Year 2009/2010. And there were 113 students. Students were divided into two groups. There were experiment class and control class. The data was collected from 3 May to 4 June 2010.To analyzed the data the writer used T-Test. After the data has been computed by T- Test formula, it revealed that Semantic Mapping technique was effective in improving students reading comprehension. It can be seen from the difference of T-Test result 2.37 and the T-table 1.99 and with df 74 at the level of significance 0.05. By consulting the T-table, T-Test was higher than T-Table (2.37 >1.99). It means the hypothesis was accepted.