Concurrent processes come into conflict with each other when they are competing for the use of the same resources. In the case of competing processes three control problems must be faced: mutual exclusion, deadlock, and starvation. The concurrency is a subject rather difficult to understand. In addition, because concurrent programs included in most of OS texts are described by pseudocode and are not being able to execute directly, almost learners are difficult to understand behaviour of concurrent programs. The purpose of this study is to propose instruction method for mutual exclusion using SDL and MSC base on graphic. In order to verify the effectiveness of the proposed materials, we compare with materials based on pseudocode. The results indicated that the proposed materials is more effective than materials based on pseudocode in teaching-learning for mutual exclusion mechanisms.