Abstract: In order to fabricate high quality concrete using poorly graded sand, six groups of concrete with poor sand gradation were prepared with different dosages of fly ash (FA) and blast furnace slag (BFS). The sand and stone compactness of the concrete was evaluated using the Andreasen equation, and the slump and compressive strength of the concrete were tested to study the effect of the dosage of fly ash and blast furnace slag on the workability and compressive strength of the concrete prepared with poor sand gradation. The results showed that the poorly graded sand and crushed stones had an adequately dense packing;both the concrete groups with 40% FA+BFS replacement and 30% FA replacement satisfied the pumping requirement;the concrete compressive strength in each group at 56 d satisfied the requirement of the strength grade, and decreased with the increasing of the dosage of fly ash. Therefore, the effect of the FA and BFS dosage on the workability and compressive strength of the concrete with poor sand gradation and dense packing is similar to that on the concrete with normal sand gradation.