An air-cooled refrigerator with an evaporator at a bottom of a cabinet, comprising: the cabinet with a bottom liner; a partition cover plate transversely arranged in the bottom liner and used for dividing an internal space of the bottom liner into a cooling chamber and a storage space, wherein the cooling chamber is located below the storage space; a return air cover arranged at a front portion of the cooling chamber, wherein, a top of the return air cover is connected to a front end of the partition cover plate, the return air cover is provided with at least one front return air inlet that communicates the cooling chamber with the storage space, and air needed for heat exchange is provided for the cooling chamber through the front return air inlet; and the evaporator, wherein the evaporator is in a flat cuboid shape, and is arranged in the cooling chamber in a manner of inclining upwards from front to back, and a front portion of a top surface of the evaporator, the partition cover plate and the return air cover define a frost-accommodating space, thereby enabling a part of air inflow from the front return air inlet to enter the evaporator from the frost-accommodating space, characterized by further comprising: a top heating wire at least arranged at the front portion of the top surface of the evaporator and configured to provide heat needed by defrosting for the evaporator, and an evaporator heat preservation part arranged between the partition cover plate and a top of the evaporator, which comprises: a filling portion with which an area region, located behind the frost-accommodating space, between the partition cover plate and the top surface of evaporator is filled; and a heating wire limiting portion extending forwards from the filling portion and provided with at least one downwards-protruding convex rib which can tightly press the top heating wire on the top surface of the evaporator. the cabinet with a bottom liner; a partition cover plate transversely arranged in the bottom liner and used for dividing an internal space of the bottom liner into a cooling chamber and a storage space, wherein the cooling chamber is located below the storage space; a return air cover arranged at a front portion of the cooling chamber, wherein, a top of the return air cover is connected to a front end of the partition cover plate, the return air cover is provided with at least one front return air inlet that communicates the cooling chamber with the storage space, and air needed for heat exchange is provided for the cooling chamber through the front return air inlet; and the evaporator, wherein the evaporator is in a flat cuboid shape, and is arranged in the cooling chamber in a manner of inclining upwards from front to back, and a front portion of a top surface of the evaporator, the partition cover plate and the return air cover define a frost-accommodating space, thereby enabling a part of air inflow from the front return air inlet to enter the evaporator from the frost-accommodating space, characterized by further comprising: a top heating wire at least arranged at the front portion of the top surface of the evaporator and configured to provide heat needed by defrosting for the evaporator, and an evaporator heat preservation part arranged between the partition cover plate and a top of the evaporator, which comprises: a filling portion with which an area region, located behind the frost-accommodating space, between the partition cover plate and the top surface of evaporator is filled; and a heating wire limiting portion extending forwards from the filling portion and provided with at least one downwards-protruding convex rib which can tightly press the top heating wire on the top surface of the evaporator. a top heating wire at least arranged at the front portion of the top surface of the evaporator and configured to provide heat needed by defrosting for the evaporator, and an evaporator heat preservation part arranged between the partition cover plate and a top of the evaporator, which comprises: a filling portion with which an area region, located behind the frost-accommodating space, between the partition cover plate and the top surface of evaporator is filled; and a heating wire limiting portion extending forwards from the filling portion and provided with at least one downwards-protruding convex rib which can tightly press the top heating wire on the top surface of the evaporator. a filling portion with which an area region, located behind the frost-accommodating space, between the partition cover plate and the top surface of evaporator is filled; and a heating wire limiting portion extending forwards from the filling portion and provided with at least one downwards-protruding convex rib which can tightly press the top heating wire on the top surface of the evaporator.