Objective:　To　prepare　the　specific　anti-elaidic　acid　polyclonal　antibody.　Method:　Polyclonal　antibodies　against　elaidic　acid　in　trans　fatty　acids　were　produced　from　rats,　which　were　injected　by　intra-peritoneal　injection　with　a　rule　of　dose　and　time　of　elaidic　acid　conjugated　with　protein.　Titer　of　serum　was　determined　by　infrared　scanning　map,　indirect　ELISA　and　protein　electrophoresis.　Result:　Titer　of　serum　in　the　forth　immunization　was　reached　to　8100,　and　competitive　ratio　was　reached　to　29.20%,　which　were　respectively　detected　by　the　method　of　indirect　ELISA　and　competitive　inhibition　ELISA.　Conclusion:　Although　the　serum　has　a　little　low　titer,　it　has　a　high　competitive　ratio.　It　suggests　that　polyclonal　antibody　against　elaidic　acid　is　really　exist　in　serum　of　immunization.　This　experiment　could　provide　reliable　experimental　evidence　and　a　theoretical　basis　for　isolation　and　purification　of　polyclonal　antibody　against　trans　fatty　acids.　Furthermore,　it　will　be　a　new　approach　to　build　an　excellent　experimental　foundation　for　the　detection　of　trans　fatty　acids　in　food　by　ELISA.