Your problem has a few things that can cause this. We fix thousands of these jobs. A little info required. Where does roof water go, how far is the ground level from basement floor, do you have a municipal storm connection. Tape a piece of 6 mm poly to the floor about 1′ 1′ tape around all the edges, see if moisture appears. Clay soil in your yard? If there is a rain water leader going into a pipe in the ground look down with a flashlight and measure the depth. What part of the country. Pictures?