In order to investigate the influence of the coexistence of clay and silt on the compression characteristics of sand, one-dimensional compression consolidation tests were carried out on reconstituted saturated sand–silt–clay mixtures with a constant initial void ratio, and the effects of fines content (FC) and clay–silt ratio (CS) on the compression characteristics of mixed soils were studied. The mechanism of the experimental results was additionally explained from a microscopic perspective. The test results show that: the compressibility of mixed soil increased with the increase in FC; the compressibility change rule of mixed soils with different CS is consistent under the same FC; the influence of CS on the e–lgp (the void ratio (e) versus logarithm of the pressure (p)) curve of mixed soil is inconsistent when FC is different: when FC = 3%, the compressibility of mixed soil decreased with the increase in CS; when FC = 7% and 10%, the compressibility of mixed soil gradually increased with the increase in CS; when FC = 5%, the compressibility of mixed soil did not show an obvious changing law with the increase in CS, and the compressibility of the specimen with FC = 5%–CS = 1 (FC = 5%, CS = 1) was the largest; when CS was same, the difference between e–lgp curves of mixed soil with different FC increased with the increase in CS. The compression model of sand–silt–clay mixtures was established, which can consider the effects of FC and CS. The reliability and applicability of the proposed model were verified by combining the experimental results of this paper and the test data of sand–clay mixture and sand–silt mixture in other literature.