The　microbial　kinetics　of　Pseudomonas　sp.　strain　DM1　during　dichloromethane　biodegradation　was　studied　by　means　of　fed-batch　culture　technique.　The　growth　of　the　bacteria　and　the　consumption　of　the　substrate　were　inhibited　severely　by　the　substrate　CH2Cl2　and　the　product　chloride　at　high　concentrations.　The　optimal　concentrations　for　reaction　were　CH2Cl2　1.2　mM　and　chloride　less　than　100mM.　When　the　concentrations　of　CH2Cl2　and/or　chloride　were　higher　than　their　restricted　values,　the　bacteria　would　die　and　autolyse,　mu　less　than　or　equal　to　0.　A　modified　kinetic　model　was　proposed　which　can　fit　the　experimental　data,　and　is　better　than　other　traditional　models.　It　consists　of　two　terms:　the　first　is　due　to　the　reversible　Monod-type　complexion　mechanism　and　the　second　is　regarded　as　an　irreversible　inhibition　effect　of　a　toxic　compound　on　the　microbial　metabolism.