Abstract: When conducting drug experiments on cells cultured in vitro, drug treatment can cause cell death, and different methods for detecting cell survival rates can impact the experimental results. This study uses HeLa cells as the experimental object and treats the cells with different concentrations of cisplatin. The cell survival rates detected with or without floating cells in the old culture medium are compared. The experimental results indicate that when using the CCK-8 method to detect the cell survival rates in 96-well and 24-well plates, the cell survival rates of the experimental group without removing the old culture medium are higher than those of the experimental group with the old culture medium removed. At a cisplatin concentration of 0.625 μM, there is a significant difference in cell survival rates between the experimental groups with and without the removal of the old medium. In 6-well plates and 100 mm dishes, a cell counter is used to detect the floating cells in the cell culture medium after drug application, and the presence of viable cells among the floating cells in the medium is found. The results suggest that the floating viable cells in the culture medium after drug treatment can affect the accuracy of the cell drug experiment results, and removing the old culture medium will remove these viable cells.