A micro flowmeter was designed based on MEMS sensor and weak signal acquisition technique. The MEMS sensor adopted VO2 thermal resistor suspended structure, which has good heat isolation performance and high sensitivity. The flow channel was made up of SU-8 gum, and this technology is simple and suitable for batch production because of low cost. The following weak signal acquisition module used super low bias current operational amplifier, aided with Guard ring protection, and 24 bit high resolution ADC to realize high resolution, low noise data acquisition through reasonable layout and ground design. The experiment shows that the entire flowmeter has favorable linearity and sensitivity in the velocity range from 0 to 30mL/min at a certain suitable offset voltage. So it can satisfy the applications in the fields such as biochemical detection, medicine and so on.