In order to explore the influence of replacing river sand with aeolian sand on filling effect and voidage of fine aggregate, the optimal replacement rate of aeolian sand for river sand with different fineness modulus in different grade distribution areas was determined. This work was accomplished through the following two aspects. The first was comparative analysis of the data of voidage, which was obtained by the replacement of aeolian sand to 9 groups of river sand with different grade distribution areas under different replacement rates. The second was simulation of fine aggregate which was operated by PFC3D discrete element software. In addition, the river sand with the same gradation as Kubuqi aeolian sand was used to carry out similar test and simulation exploration. By comparing the previous test results, the influence factors of the grain shape of the aeolian sand in the Kubuqi desert on the voidage of fine aggregate under different fineness modulus river sand and different replacement rates were determined.