The invention discloses a water-blocking medium voltage aluminum alloy power cable which comprises an insulating cable core and an outer wrapping layer, wherein one or more insulating cable cores are provided; the insulating cable core is wrapped by the outer wrapping layer so as to form the water-blocking medium voltage aluminum alloy power cable. The cable is characterized in that each insulating cable core comprises an inner aluminum alloy conductor core (1), an inner shielding layer (2), an insulating layer (3), an outer shielding layer (4), a semiconductor resistor water-blocking zone (5) and a seamless metal sleeve (6) from inside to outside in sequence; the outer wrapping layer comprises a winding and wrapping layer (7), an inner protective layer (8), an armored layer (9) and an outer protective layer (10) from inside to outside The aluminum alloy power cable disclosed by the invention is made of an aluminum alloy material, the inner aluminum alloy conductor core is high in yield strength, small in resilience value, free of memory effect and easy to install, and compared with a copper core cable of the same mass, the cable is small in resistance, and the cost of the alloy material is smaller than that of copper.