Abstract: Water mist flux is one of the key factors in flame extinguishment, so total flux was usually discussed in former research works. In order to distinguish the portion of water mist that has a direct influence on the flame or fuel, effective flux was defined based on the current conception of water mist flux. Collecting tubes and the APV (adaptive phase/ Doppler velocimeter) system are two ways currently employed to measure water mist flux. In order to measure the unstable water mist flux and improve the tube-collection method, a water mist generating system and an electronic balance were set up to validate the means of using electronic balance to measure the flux. It was proved that electronic balance can measure flux density effectively and in real-time. Meanwhile, fluxes of different heights have a good correspondence with the results of theoretic calculation. Ununiformity of the water mist field is the reason for the slight difference in results between the experiments and calculation. Some expressions were presented to calculate the dimensional distribution of effective flux density. A lot of fire suppressing experiments can be omitted using the calculation.