The effect of different proportion of engineering muck and fly ash on the physical properties of artificial aggregates with high strength and low water absorption was studied. Moreover, the mineral composition, microstructure and porosity of artificial aggregates were characterized by X-ray diffractometer, X-ray computed tomography (X-CT), mercury intrusion porosimetry and scanning electron microscope. The results indicate that the density and strength of artificial aggregates increase firstly and then decrease with the increase of fly ash content. However, the water absorption variation shows the opposite trend. When the fly ash content is 50% (mass fraction), the high strength and low water absorption artificial aggregates with an apparent density of 2.17 g/cm3, compressive strength of 22.88 MPa, and water absorption rate of 0.055% are prepared. The decrease in the strength of artificial aggregates and the increase in water absorption is mainly due to the increased porosity caused by the insufficient liquid phase. High Al2O3 content in the raw material hinders the formation of a liquid phase, which degrades the physical properties of artificial aggregates.