The experimental prototype described in this research is a reciprocating active magnetic refrigerator with two permanent magnets and two active magnetic regenerators. Extensive tests have been carried out to measure the cooling performance of this prototype with nitrogen or helium as the heat transfer fluid. The prototype can produce a relatively large cooling power and a wide temperature span even at low charging pressure of the heat transfer gas. The lowest no-load cooling temperature of 3.2 °C, a maximum temperature span of 24.6 K and a maximum cooling power of 20.5 W around 4.5 K were achieved with helium as the heat transfer fluid at a pressure of 1.2 MPa, a frequency of 0.6 Hz, a phase angle of 90° and a gas displacer stroke of 180 mm. The influences of operating frequency and the heat transfer gas charging pressure on the refrigeration performance were experimentally investigated and discussed.