The present invention relates to a micro-volume liquid ejection system, including an air pressure module, a micro-ejection unit which is connected with the air pressure module by means of pipes, and a control circuit which is connected with the air pressure module and the micro-ejection unit respectively. In the present invention, due to air is used as the pressure medium, on one hand, as the sample does not contact with the pressure regulating module, the efficiency of cleaning process is improved, on the other hand, the volume of the sample needed in the sample ejecting process is only equal to the cavity-dimension of the micro-ejection unit by not need to fill the whole pipe with liquid. During the sample ejecting process, it is not need to regulate the pressure. After the sample ejecting is finished, the sample can be put into its original place, so as to greatly save the sample. The present invention is connected with the manipulator, so as to sample from the sample plate, eject sample and clean the pipes automatically, and it can also dispense a multiplicity of samples to micro-array substrate conveniently. The present invention can be used for transferring or dispensing the micro volume liquid of nL grade and L grade widely, and all kinds of the micro-volume liquid including biological liquid.