Unsteady natural convection heat transfer of incompressible fluid in an inclined cavity filled with saturated porous medium is studied numerically.The temperature of the cold sidewall maintains constant and the temperature of the opposite sidewall varies sinusoidally with time.The Brinkman-extended Darcy model and SIMPLER algorithm are adopted.Comprehensive numerical solutions are acquired at a fixed Prandtl number Pr=1 and a Rayleigh number Ra=10⁶.The inclination angle of the enclosure α varies from 0° to 90°.The effects of α and dimensionless oscillation frequency f on the natural convection are analyzed.The maximum heat transfer is reached at f=60π and α=43°.