Micro-pump used in domestic medical and biochemical field relies on import and the technique is monopolized. In order to solve this problem, a micropump which is mainly used in invitro diagnostic analyzer is designed. The innovative design of threeposition fourway valve controlled by stepping motor was adopted, which greatly improved the precision of micropump. And the structure simulated design of each module of micropump in Solidworks software was carried out. The performance of the whole motion module was analyzed by ADAMS software, and the rational performance of the micropump was verified. The injection accuracy and injection volume of the micropump were also calculated. The computed analysis show that his structure design has high precision, which simplifies the fluid system of the in vitro diagnostic analyzer, and provides a theoretical basis and reference value for the medical industry.