A magnetic flux detection apparatus and a system with the magnetic flux detection apparatus are provided. The magnetic flux detection apparatus includes the magnetic material, at least one heated or cooled magneto caloric effect material (MCEM), a permanent magnetic element, at least one magnetic sensing element, and at least one amount of magnetic flux or magnetic flux path. The heated or cooled magneto caloric effect material is disposed to the magnetic material. The amount of magnetic flux or magnetic flux path is formed and passing through the permanent magnetic element, the cooled magneto caloric effect material, and the first portion of the magnetic material. A magnetic sensing element senses the amount of the magnetic flux or the magnetic flux path for outputting a sensing voltage and a corresponding sensing voltage value so as to apply the best thermal energy-applying algorithm into the magnetic system to output power efficiently.