The　mechanical　behaviors　of　sand　are　heavily　dependent　on　its　relative　density:　the　dense　sand　exhibits　softening　strength;　on　the　contrary,　the　loose　one　displays　hardening　strength.　Furthermore,　the　relative　density　is　determined　based　on　the　maximum　and　minimum　void　ratios.　The　maximum　and　minimum　void　ratios　are　commonly　obtained　by　using　the　maximum　and　minimum　densities,　ignoring　the　effects　of　test　methods　and　clay　contents　in　sand.　The　maximum　and　minimum　void　ratios　are　tested　by　considering　three　different　sized　groups　of　sands　with　various　clay　contents.　It　is　shown　that　the　minimum　dry　density　can　be　attained　in　a　measuring　cylinder　with　low　rotation　speed.　In　addition,　it　is　suggested　that　the　maximum　dry　density　of　fine　sands　should　be　measured　with　the　250　mL　compaction　cylinder　combining　vibration　with　hit,　while　the　1000　mL　compaction　cylinder　is　suitable　for　medium　and　coarse　sands.　The　results　also　show　that　the　void　ratio　decreases　with　the　increase　in　clay　contents　(less　than　30%),　while　there　is　a　linear　relationship　between　the　clay　contents　and　the　void　ratio　of　sands.　However,　the　maximum　void　ratio　of　sand　decreases　with　increasing　content　of　silty　clay　and　clay,　and　increases　with　increasing　content　of　kaolin　clay.　©　2018,　Editorial　Office　of　Chinese　Journal　of　Geotechnical　Engineering.　All　right　reserved.