Coagulation test, in principle, is an immunodiagnostics technique, in which immunoglobuline G of antibody is bound to protein A from Staphylococcus aureus. The aim of study is to develop a rapid test kit for detecting iridovirus infection in fish. Method was summarized as follows: (1) vaccine of iridovirus was injected to rabbit four times with a dosage as 0.5 mL, 1 mL, 2mL, 3 mL each week. Serum was collected at the fifth week as a coagglutination test kit; (2) through the positif polymerase chain reaction (PCR) test, the kidney and spleen sample infected with iridovirus are homogenized by using the phosphate buffered saline (PBS) solution of pH 7.2 with ratio 1:2 (W/V); (3) the supernatant material is collected after centrifugation at 8,000 rpm for 15 min; (4) filtrate/supernatant from sample was dropped on a slide an added with coagglutination test kit with the same volume (1:1); (5) the agglutination observation is done after the 30, 60 and 90 min incubate at room temperature. The coagglutination test gave positive result in 25% of the test samples.