In this note, we consider the radial symmetry property of rotating vortex patches for the 2D incompressible Euler equations in the unit disc. By choosing a suitable vector field to deform the patch, we show that each simply-connected rotating vortex patch D with angular velocity Ω, Ω ≥ max{1/2, (2l 2 )/(1 − l 2 ) 2 } or Ω ≤ −(2l 2 )/(1 − l 2 ) 2 , where l = sup x∈D |x|, must be a disc. The main idea of the proof, which has a variational flavor, comes from a very recent paper of Gómez-Serrano-Park-Shi-Yao, arXiv:1908.01722, where radial symmetry of rotating vortex patches in the whole plane was studied.