The invention discloses a bio-assay detection method. The method comprises the steps of 1, continuously acquiring frame pictures of a face through an image acquiring device; 2, detecting the acquired continuous frame pictures through a trained facial expression detecting unit, a face posture detecting unit and an expression change detecting unit; 3, determining that the face is a true human face if more than two groups of basic actions change according to the detection result in step 2, and otherwise, entering step 4; 4, randomly selecting a group of basic instructions from state element sets of the three detecting units, and prompting a user of finishing the group of basic instructions within the specified time; if that the user finishes the basic instructions is determined according to the detecting results of the three units, determining that the face is the true human face, and otherwise, determining that the face is a false face. With the adoption of the method, the effective deformation of the human face can be accurately caught and accurately detected, so that the true human face and the false face can be distinguished, and the invasion of a human face recognition system can be reduced.