Non-isothermal flow through a rotating curved duct with square cross section isstudied numerically by using the spectral method, and covering a wide range of the Taylornumber, Tr, 0 ≤ Tr ≤ 2000 and Dean number, Dn, 0 ≤Dn ≤ 2000. A temperature difference isapplied across the vertical sidewalls for Grashof number Gr = 500, where the outer wall is heatedand the inner one cooled. The rotation (Coriolis force) of the duct about the center of curvature isimposed. The Steady solutions are obtained by using Newton-Raphson iteration method and theDean numbers are also discussed in detail. Then, in order to investigate the non-linear behaviorof the steady and unsteady solutions, there is no stable steady solution, time evolutioncalculations as well as power spectrum of the periodic oscillations are obtained, and it is alsofound that for larger Dn, the unsteady flow undergoes in the scenario“steady→ periodic → chaotic → steady”, if Tr is increased. Finally spectral analysis and phasespace are found to be very useful investigation of the Non-isothermal fluid flow behavior.