The Purpose of this research is to build a real-time flight simulator for quadrotor system and verify if the simulator runs in real time. The simulator was constructed by writing the mathenatical models of quadrotor dynamic in MATLAB/ simulink. Using xPC Target software environment, three PCs were set up to work in sync to make the simulation run in real time. This paper shows several simulation esults of the quadrotor dynamic in three flight diractions. These result validate the stable performance of PD controller being used. AT the same time it can be revealed that the simulation runs in real time by observing the percentage processing usage of the computer as function of simulation time. The simulator can be very useful for researches to understand the character of the quadrotor system being depeloved and for pilots to complete a mission using the quadrotor system