In this study, we successively and parallelly slide a solvent strip on a polydimethylsiloxane microwell array to dilute the solution within the microwells. A total of 60 concentration gradients were generated one by one along the sliding direction within minutes while simultaneously forming 60 microwells with the same concentration perpendicular to the sliding direction. Using theoretical calculations, simulated predictions and experimental verification, we could regulate the concentration gradient on the microwell array by tuning the parameters of the sliding head and sliding speed. Afterwards, we cultured human non-small cell lung cancer cells and produced an anticancer drug concentration gradient on the microwell array by this sliding method. The cell viability was examined to demonstrate the potential of this method for high-throughput cell-based drug testing and screening, and this open microwell array method may enable further analysis during a drug-screening process.