Abstract: A new enzyme immunoassay system, Urease-antibody conjugate ELISA and its application in the diagnosis of schistosomiasis japonica was reported. Urease was extracted and crystallized from jack bean meal. Urease-conjugate was prepared by the one-step glutaral-dehyde method. The substrate solution was made up with bromocresol purple and urea. Urease catalyzes the hydrolysis of urea to NH3, and pH shift causes a vivid colour change from yellowish to purple. This enzyme-substrate system offers a number of advantages, the substrate is stable, easy to obtain and without harm to human beings, and the colour change between negative and positive reaction is unmistakable. As urease is unaffected by the presence of the preservative sodium azide in reagents, the substrate may be prepared and stored until use. As urease does not exist in mammalian tissues, no endoge-neous activity occurs when urease-antibody conjugates are used to detect antibodies. A total of 36 normal persons and 36 schistosomiasis patients were tested by ELISA using urease-conjugate, the preliminary results showed that both sensitivity and specificity are promising.