A liposome immunoassay comprising the steps of reacting an analyte antigen, a liposome bearing antibody comprising a first antibody to the analyte antigen and a liposome encapsulating a marker therein linked to the antibody, and a second antibody to the analyte antigen to form an antigen-antibody complex, releasing the marker from the liposome in an amount depending on an amount of the analyte antigen in the presence of a complement, and measuring the released marker to determine the analyte antigen, characterized in using a third antibody capable of binding directly or indirectly to the second antibody and having an ability to activate the complement; andA kit for liposome immunoassay comprising at least one of; (1) an liposome bearing antibody comprising a first antibody to an analyte antigen and liposome encapsulating a marker therein linked to the antibody; (2) a second antibody to the analyte antigen; (3) a third antibody capable of binding directly or indirectly to the second antibody and having an ability to activate a complement; and (4) the complement.