A silver-modified piezoelectric quartz crystal probe was involved in constructing piezoelectric biosensor for detection of hydrogen sulfide positive genus which releases hydrogen sulfide during metabolism. This biosensor was based on the special affinity of hydrogen sulfide on silver and the classic piezoelectric quartz crystal gas-mass response. The results indicated that this biosensor showed an excellent specificity to distinguish the hydrogen sulfide positive genus from the negative. The optimum concentration of cysteine in culture medium was obtained to be 0.05%. The biosensor avoided direct contact of the probe with culture medium，which could limited most influence in the liquid-mass response. This method would be expected to use in the automated detection of hydrogen sulfide positive genus during cultivation.