Abstract: In order to achieve high-precision motion control performance in multi-link flexible joint robots, we present a complete dynamics model, which includes the coupling between the links and the actuators, a LuGre dynamic friction model, and backlash. Based on this dynamics model, we propose an adaptive backstepping control method with observers, in which non-measurable terms are estimated and compensated online. Our theoretical analysis proves the convergence of the observer and the stability of the closed-loop system. The simulation results of this method on a 3-DOF flexible joint robot verify the effectivity of the observer, and demonstrate that the proposed controller can reduce link errors and achieve good trajectory tracking performance.