The invention relates to an oil separator, a heat exchange device, an electric appliance and a control method of the oil separator. The oil separator comprises a shell, an air pipe and a flow guide part. A separation cavity is formed in the shell. The air pipe comprises an air inlet pipe and an air outlet pipe, the inner end of the air inlet pipe communicates with the separation cavity, the outer end of the air inlet pipe communicates with the compressor, the inner end of the air outlet pipe extends into the separation cavity, and an oil storage space is formed in the lower part of the separation cavity. The flow guide part is connected into the shell to separate the separation cavity, the flow guide part is located between the inner end of the air inlet pipe and the inner end of the air outlet pipe, the flow guide part is provided with flow channels, each flow channel comprises a first opening formed in the first surface of the flow guide part and a second opening formed in the second surface of the flow guide part, the distance between the second openings and the inner wall of the shell is smaller than that between the first openings and the inner wall of the shell, and the second openings deviate from the inner end of the air outlet pipe. The flow guide part has the flow guide effect, the proportion of oil entering the air outlet pipe can be greatly reduced, after the oil is discharged from the second opening and condensed, most of the oil is gathered in the oil storage space, the oil-gas separation efficiency can be improved, and the oil shortage problem of the compressor is solved.