The energy separation measurements were made of a vortex tube with a bend. The results are summarized below. (1) The influence of the bend may be neglected, for a bend with R=γ_w and α≤15°, and for a bend with R≥5γ_w and α≤90°, where R, γ_w and α are the radius of curvature, the inner tube radius and the turning angle of the bend respectively. (2) For α>15° and R=γ_w, the tangential velocity and the total temperature gradient of a spiral flow decrease remarkably at the bend, therefore the energy separation in the spiral flow drops suddenly. (3) The larger the value of α, the larger the total enthalpy of air in the central reverse flow near the nozzle openings and also the mass flow rate of air passing from the nozzle openings directly to the cold end orifice. These facts decrease the energy separation in the bent vortex tube with a small radius of curvature.