In order to improve the performance of rotating-wing heat meter and reduce the cost of development, the three dimensions numerical calculations of the internal fluid characteristic within a heat meter are carried out based on the standard k-ε turbulent mode, the finite volume method and SIMPLE algorithm. The speed field and pressure distribution within heat meter are analyzed according to the result of numerical calculation. The flux measurement accuracy and pressure loss of basal meter are forecasted according to the calculated results. The calculated results of the impeller's rotating speed are compared with experimental results and prove the validity of the calculated results. This researches shows the calculated results can forecast the performance parameters of basal meter and can provide great help for design of the heat meter.