Abstract: At present, many grass-roots units in Chin still can not test HBsAg in patients, f'or solving this problem, we construcked bispecific antibody for detection HBs Ag using chemical recombination technique.Using this reagent,the rapid whole-blood immunoassay kits were combined(designed JKD).Using the kits, 1- 2.5ng/ml of HBs Ag was tested in whole-blood of patients. Paired test was perfomed in JKD with EIA and PHA kits and the according rates was 98.3% and 98.7%, respectively. HlBs Ag in different population were detected. 16 cases of HBsAg postive by EIA were 100% postive with JKD kits.The postive rates of HBs Ag in viral hepatitis patients was 64.6%(51/79),no one postive detevtable in 73 blood donors, and in genaral population, positive rate of HBs Ag was 3.8%(2/52).The results in this paper indicates JKD kit not only simplyer and faster bnt also have very good senstivity and specificity. The kits can be used in bed-side test of patient, screening of blood donors and epidemiological survey. In addtion the kit especially suitble for application in the grass-roots units in china.