Since 1980s, piezoelectric quartz crystal microbalance (QCM) has been interested for biosensor application (1). It was the poor detection limit (~ng level) of the QCM system that restricts further development in biosensor application, even though the QCM system has the low cost advantage. Entering the year 2000, the detection limit of QCM can reach to pg level, with similar cost of prior QCM system due to the progress of microelectronic industry. This high sensitive QCM biosensor system can expand its applications in library screening and confirmation for combinatorial chemistry; and has the potential in clinical application.