Frictional effects on instrumented indentation of strain hardening solids were examined. Finite-element simulations were carried out to study the effects of friction coefficient on the two representative indentation test methods: Ma method and Oliver-Pharr method. It is found that for different friction coefficient from 0 to 0.2, the test accuracy of elastic modulus derived by Ma method or Oliver-Pharr method is evidently sensitive to the values of friction coefficient; While the friction coefficient is > 0.2, the sensitivity of test accuracy tends to be stable. Comparing the test accuracy of the two methods, Ma method are better than Oliver-Pharr method in terms of test accuracy and stability. Ma method is recommended for instrumented indentation test. The experimental data of two aluminum alloys shows that, considering frictional effects, the amendment for Oliver-Pharr method is an effective method to improving its test accuracy.