Abstract: The uniaxial unconfined compressive strength tests are performed to investigate the strength properties of clay-gypsum cementation materials after curing of 12 to 336 hours. The initial setting time and change processes of uniaxial unconfined compressive strength with curing time are obtained. Meanwhile, the uniaxial unconfined compressive strength tests on clay-gypsum cementation materials mixed with gravels with diameter of 2 to 5 mm are conducted to study the effect of gravel combinion. The test results show that the initial setting time is short and less than 15 minutes. The change in the uniaxial unconfined compressive strength of the samples with curing time can be divided into three stages: early, medium and late stages, that is, strength change, obvious increase and stabilization stages. The early strength of the sample with gravels does not decrease and the change process of the medium and late strength is similar to that of the sample without gravels. However, its strength obviously increases earlier and medium stage is longer. The late stable strength of the sample with gravels is much larger than that of the sample without gravels.