A QCM-based SELEX was developed to select ssDNA aptamers against Salmonella typhimurium. The binding behavior was monitored and recorded in real-time by QCM. The selected aptamer was used as a ligand for the development of a QCM-based aptasensor. The aptasensor was able to detect 103 CFU/mL of S. typhimurium within 1 h.