This study is virtually intended to comprehend influential Mathematical Realistic Learning Approach (MRL) upon mathematical communication aptitude of Junior High School RA Kartini Sei Rampah, to overview has the interactive learning approach, and Initial Mathematical Cognition (IMC) found upon mathematical communication power and positive aptitude. Typically this observation regarded as quasi-experiment. Populated Samples took place on Junior High School R.A. Kartini Sei Rampah. With 34 students of VII-3 held as the class of experiment and 34 students of VII-6 held as the class of control by purposive sampling method. Analyzed data applied ANOVA 2 trace. The proceeds: (1) There is influential approach of (MRL) found upon mathematical communication aptitude, (2) There is IMC approach found, (3) There is an interaction between learning approach and Initial Mathematics Cognition which influencing mathematical communication power, and (4) There is found not any interaction between learning approach and initial mathematics cognition in forcing positive aptitude in which learning working out with MRL approach more better than conventional learning approach.