Abstract: In order to measure the density of cryogenic fluids in different states，an experimental setup for density measurement of cryogenic fluids by dielectric constant method has been designed and fabricated to measure the ensity of deuterium and oxygen，with a two-stage G-Mcryocooler as the cold source.The system is applicable for the temperature range of 15～300 K，and pressure range of 0.01～0.3 MPa.The experimental liquid is obtained through liquefaction of the gas by the cryocooler and then stored in the sample fluid test cell，in which the parallel plate capacitor is positioned.The test cell is embedded with an optical window，which can be used to observe the formation of liquid and its level during the cooling process.The densities of liquid deuterium and liquid oxygen under controlled pressure and temperature have been measured.The liquid phase measurement agree with the experimental data in literature and the NIST reference data within± 0.5%，which meets the accuracy requirement of high quality p-ρ-Tproperty measurement.