The weakness of the conventional box counting algorithm in measuring the dimensions of fractals is analyzed. A novel improved box counting method is proposed by introducing a new parameterη

which is the ratio of fractal object's length in a box over the edge length of the box. For fractals having infinite self-similar levels

η is also infinite which has no meaning in mathematics. But the fractals existed in the real world all have their scaling limits

soηis meaningful in practical measurement. Its advantage is proved by the examples in the paper

and its limits are also pointed out. The uncertainty in measuring the fractal dimension using box counting method is discussed

and the corresponding means to overcome them are also proposed. Planar laser-induced fluorescence technique was employed to measure the concentration field in the near wake region of circular cylinder. Turbulence non-turbulence interfaces were extracted from these images

and the new box counting algorithm is used to measure the fractal dimension of these interfaces. The measured results agree with those of other researchers

and it is found that the fractal dimensions vary little with time in an unsteady flow field.