A constant solid state flow velocity/mass sensor has been fabricated and its characteristics were measured according to flow velocity and fluid temperature. Parameters of the sensor circuit were obtained by simulation using finite difference method. Sensitivity was 10mW/(cm/sec) in the range of flow velocity 0-45cm/sec and response time was within two seconds. For the experiment of fluid temperature variation, the sensor output was compensated at the rate of temperature variation $0.1^{circ}C/min$, however, with the rate of $0.2^{circ}C/min$ it took two minutes to be compensated. Since it is not quite often to have such a rate of temperature variation of $0.2^{circ}C/min$ or more, the developed sensor output can be used for most applications to detect small amount of flow-rate.