Title:From MW spiral arm tracers to the actual pattern (invited talk) Abstract: If it is clear that our Galaxy is a spiral galaxy, its arms structure is still a matter of debate: number of arms, pitch angle of the arms, design of arms ... The structure determination of our Galaxy rest on the determination of the spiral arm tracers distance. In this context I will review the classical tracers of the spiral arm and I will present the different model of our MW and the observational perspectives.