Goals to be achieved by the researchers, is to know the results of the implementation of the mastery content services in improving student achievement of class VII SMP Negeri 2 Metro in the academic year 2013/2014. The study design using action research applied in guidance and counseling services. Subjects in this study, researchers took student class VII SMP Negeri 2 Metro in the academic year 2013/2014. Of the 24 students there are 10 students who experienced low mathematics achievement 41.66%. Results from this study that through mastery of content services provided by BK teachers can improve student achievement class VII SMP Negeri 2 Metro. There is an increase in student achievement in the first cycle seen from the average percentage that is equal to 27.5% and the second cycle by 75%, resulting in an increase of 47.5%.