A　mathematical　model　of　competition.　type　lateral　flow　immunoassay　(LFIA)　was　developed　to　describe　the　dynamic　process　of　LFIA.　The　competition.　type　LFIA　was　divided　into　two　categories:　TwA-competition.　type　LFIA　and　TnA-competition.　type　LFIA.　On　the　basis　of　the　developed　model,　the　COMSOL　software　was　exploited　to　simulate　the　dynamic　process　of　LFIA.　The　simulation　result　demonstrated　the　relationships　between　the　concentrations　of　substances　on　the　test　and　control　lines　and　the　influence　factors.　In　particular,　the　influence　factors　in　the　TwA-competition.　type　LFIA　included　the　concentrations　of　target　analyte　A　(0-20　mol/L)　and　reporter　particle　P　(0.01-100　mol/L),　and　the　position　of　the　test　line　(5-20　mm).　On　the　other　hand,　the　influence　factors　in　the　TnA-competition.　type　LFIA　included　the　concentrations　of　target　analyte　A　(0-20　mol/L)　and　reporter　particle　P　(0.　01-100　mol/L),　and　the　porosity.　Experiment　result　showed　that　the　developed　model　could　be　used　to　explore　the　influence　of　the　parameters　on　the　test　results,　and　optimize　the　performance　of　LFIA.