A high capacity free piston Stirling cooler(FPSC) was designed for 200 K low-temperature fridge.In order to study the characters of the prototype,a performance test bench was built.Frequency characteristics of the compressor and the expander were investigated in detail.The effects of charged pressure and cooling temperature on the compressor resonance frequency were tested.Furthermore,the influences of the displacement phase shift and the expander natural frequency on its operating frequency were experimentally studied.The static loss of the cooler was tested by multipoint hot load static rewarming method.The helium and the mesh screens are proved to have little affection on the static loss in virtue of thermal conduction.The maximum cooling capacity of the prototype can reach 40 W at 200 K with 250 W input.