Based　on　the　surface　plasmon　resonance　imaging　(SPRi)　instrument,　we　established　a　new　method　of　analyzing　morphine　in　urine　by　processing　a　calibration　curve.　According　to　an　inhibition　immunoassay,　gradient　concentration　of　morphine　and　morphine-BSA　fixed　on　the　chip　competitively　combine　with　morphine　antibody　on　the　chip.　Given　the　three　mathematical　models,　the　data　of　SPRi　signals　generated　from　SPRi　with　morphine　was　processed　to　obtain　the　calibration　curve.　Ultrafiltration　was　used　to　pretreat　blank　urine　samples　with　adding　morphine,　and　then　investigated　the　advantages　and　disadvantages　of　each　model.　With　a　limit　detection　of　6.57　ngmL-1,　the　method　and　mathematical　models　can　provide　robust　support　for　SPRi　sensors　used　in　further　environmental　detection,　such　as　the　epidemiological　study　of　sewage.