Image interpolation methods used to improve medical image quality on display device or in the field of lossy image compression wherein some pixels. Therefore

image interpolation methods have occupied a peculiar position in medical image processing and many interpolation methods have been presented. But the image processed by the conventional interpolation methods (such as linear interpolation

double-linear interpolation etc.) have lost the image texture and caused smoothness effect. To avoid these effects

many scholars look for other interpolation methods. Through survey the greylevel of the natural image

paper has proved the greylevel of the natural image meet the isotropic fractional brownian of random(FBR). In this paper

we present processing head CT by fractal interpolation. And we have given the method to compute the correlative parameter. To evaluate the processed image quality

we introduce fuzzy degree and fuzzy entropy from fuzzy mathematics. According to the property of fuzzy degree and fuzzy entropy

the high quality image has less fuzzy degree and fuzzy entropy than the low quality image. Simulation results show that this new method has better performance than the other interpolation methods.