Provided is a process for continuously preparing a polyolefin composition. The process for continuously preparing a polyolefin composition comprises polyolefin and carbon black in an extruder device, the process comprising supplying polyolefin in form of a polyolefin powder and carbon black to a mixing device; measuring the flow rate of the polyolefin powder supplied to the mixing device or measuring the flow rate of the polyolefin pellets prepared in the extruder device; adjusting the flow rate of the carbon black to the mixing device in response to the measured flow rate of the polyolefin powder or adjusting the flow rate of the polyolefin powder to the mixing device in response to the measured flow rate of the polyolefin pellets; melting and homogenizing the mixture within the extruder device; and pelletizing the polyolefin composition.