Blood smear test is the basic method of blood cytology and is also a standard medical test that can help diagnose various conditions and diseases. Morphological examination is the gold standard to determine pathological changes in blood cell morphology. In the biology and medicine automation trend, blood smears' automated management and analysis is very necessary. An online blood smear automatic microscopic image detection system has been constructed. It includes an online blood smear automatic producing part and a blood smear automatic microscopic image detection part. Online identity authentication is at the core of the system. The identifiers printed online always present dot matrix digit code (DMDC) whose stroke is not continuous. Considering the particularities of DMDC and the complexities of online application environment, an online identity authentication method for blood smear with heterological theory is proposed. By synthesizing the certain regional features according to the heterological theory, high identification accuracy and high speed have been guaranteed with few features required. In the experiment, the sufficient correct matches between the tube barcode and the identification result verified its feasibility and validity.