Based on the Archimedes law, the fully weathered granite specimen in nanyue area were disintegrated test in undisturbed, drying, air drying, with liners supporting different status with the largely homemade fully weathered granite disintegration instrument.The least squares method was used in experiments, the linear equations of the measuring cylinder reading and disintegration instrument drainage volume was matched, the reading error was reduced with the buoy initial reading method was improved. The test results show that the whole disintegration process of specimen is divided into three stages: the biggest collapse rate is the second stage,the second is the first stage, and the third stage is minimum. The disintegration time is affected by filtration methods directly, specimen dehydration is severe and disintegration time is the shortest in drying condition, with having the protection of tube supporting, the contact area of the water and the specimens is reduced, prolong the disintegration of the specimens.The results of the study provide the reference basis for the civil engineering construction in nanyue fully weathered granite area.