In order to investigate the effects of silica fume (SF) dosing and rubber particle size on the creep properties of cement mortar, orthogonal tests were carried out using 16 groups of specimens designed to analyse the unconfined compressive strength, creep properties and microscopic characteristics of cement mortar with different silica fume dosing and different rubber particle sizes, respectively. The results showed that the rubber particles would reduce the unconfined compressive strength and increase the creep deformation of the mortar, and the strength of the mortar recovered and the creep deformation decreased after the addition of SF. In the creep test, both rubber mortar and ordinary mortar experienced three levels of loading, and the creep of rubber mortar lasted longer, while the addition of silica fume significantly increased the load level at which the specimen suffered damage. The parameters of the Burgers model were identified based on the test data of the decelerated creep stage and the isokinetic creep stage, and it was found that they were in good agreement.The microstructure and fine-scale modelling show well the synergistic mechanism of rubber and silica fume on the creep performance of mortar.