Venous catheter setter capable of drawing and detecting return blood

The present invention relates to an intravenous tube fixer capable of drawing and testing returned blood. It mainly includes a drawing-testing unit capable of producing suction action and a needle group. Said needle group has a needle body communicated with said drawing-testing unit, a tube seat which can be removably connected with said drawing-testing unit, and a flexible tube through which theneedle body can be passed. Said invention also provides the concrete working principle and its operation method.