Animals' regional femur blood (F) alteration was studied under an inadequate decompression by using the inhaled isotope ¹³³Xe washout method. Results showed that the average F on left and right side of minipigs' femur decreased from 15.4±1.8 and 16.9±2.0ml/ (100g•min) (before exposure) to 10±1.8 and 11.1±1.6ml/ (100mg•min) (after expposure for 1.5 h under the pressure of 0.5 MPa and then decompression to normal with the rate of 0.03〜0.04 MPa/min) , respectively; the blood flow of hematopoietic marrow tissues (f₁) on both sides also decreased from 19.3±2.0 and 22.1±1.9ml/ (100mg•min) to 13.9±1.4 and 13.8±1.0ml/(100mg·min) . The exact same alteration also happened in the experiment on New Zealand rabbits. It indicates that inadequate decompression in hyperbaric exposure can give rise to decrease animals' bone blood flow and insufficient bone blood supply serves as one of the reasons for causing decompressive osteonecrosis.