The flow regime transitions in a gas-solid fluidized bed were studied for the first time using a micro-foil heat flux sensor. The time series of heat flux signals was analyzed by statistical and state space methods. The experimental measurements were performed in a lab-scale gas-solid fluidization column. Four different flow regimes, i.e., fixed-bed flow regime, bubbling-flow regime, slugging-flow regime, and turbulent-flow regime, and three intermediate transition velocities, i.e., minimum fluidizing velocity or minimum bubbling velocity, minimum slugging velocity, and minimum turbulent velocity, were successfully identified. The method based on the analysis of heat flux sensor measurements allowed to determine accurately the different flow regimes and the transition velocities.