There was a problem of female students to engaging regular physical activity, sport computation, feeling weak. no opportunity to participate aerobic exercise. The purpose of this study was to find out the effect of aerobic exercise on selected physical fitness components and physiological variables of female students in Addis Zemen general secondary school.. To achieve the purpose of the study purposive sampling and lottery method is used to selected 56 students (experimental 28 and control groups 28). The study employed quasi Experimental research design. The participants were exercised for 12 weeks, three days in a week, for 45-60 minutes per session on walking, jogging, skipping rope and running and other aerobic exercises. The control group did not perform Aerobic class. The selected health related fitness’s were Cardiovascular endurance was measured by 1.5 mile run, muscular strength was measured by wall sit , flexibility was measured by sit and reach, and physiological variables resting heart rate measured by countering resting heart beats per minute, systolic and diastolic blood pressure is measured by using sphygmomanometer . Before the training program pretest was taken for each variable and at the end of the training also post-test was taken from the participant. Raw data was statically analyzed by using paired sample t-test by using Statistical Package for Social Sciences version 20 at the p-value of (P<0.05). After the analysis of the pretest and posttest mean difference of cardiovascular= 1.9614, strength= -15.179, flexibility= -7.396, resting heart=7.107, systolic blood pressure=11.071 and diastolic blood pressure= 9.286, the experimental group was improved significantly. But, no significant improvement were found in all selected variables of control group (p>0.05).the formulated hypothesis is accepted. Result. Aerobic exercises was effective and beneficial for the improvement of female students on some selected physical fitness component and physiological variables' in Addis Zemen secondary school female students Key words:- cardiovascular endurance ,muscular strength. Flexibility, resting heart rate, systolic and diastolic blood pressure and Aerobic exercise.