Multi-threading is a methodology that has been extremely used. Modern software depends essentially on multi-threading. Operating systems, famous examples, are based on multi-threading; a user can write his document, play an audio file, and downloading a file from internet at the same time. Each of these tasks called a thread. A common problem occurs when implementing multi-threaded programs is a data-race. Data race occurs when two threads try to access a shared variable at the same time without a proper synchronization. A detector is software that determines if the program contains a data-race problem or not. In this paper, we develop a detector that has the form of a type system. We present a type system which discovers the data-race problems. We also prove the soundness of our type system.