Abstract: The permeability coefficient of unconfined aquifer in the underground research facilities (URF) at CIRP's test field was obt ained by Hvorslevr's slug test which seems to be an only appropriate option that in the condition of thin aquifer, poor water quantities, limited space for ongoing test of nuclides migration, we can not adopted any pumping test ot injection test.The aquifer medium is made of loam.The bot tom of URF is 6 meters higher than the bottom of the aquifer.The impulse capacity of the test was so small that we can neglect the impact on test results from the south of the aquifer.The aperture of bore hole for test designed was closed to the inner diameter of well pipe theref or the influence of the structure of bore hole on test results was reduced.Comparison of the results of laboratory test (4.1×10^-4~8.2×10^-4cm/s) in which undist urbed soil column was used and the permeability coefficients result acquired by the slug test (4.72×10^-4, 6.58×10^-4cm/s) was same in magnitude.