Nucleate site distribution plays an essential role in nucleate boiling process. In this paper, it is pointed out that the size and spatial distribution density of nucleate sites presented on real boiling surface can be described by the normalized fractal distributlon function, and the physical meaning of parameters involved in some experimental correlations proposed by early investigations are identified according to fractal distribution function. It is further suggested that the surface micro geometry characteristics such as the shape of cavities should be described and analyzed qualitatively by using fractal theory. K e y w o r d s : n u c l e a t e s i t e , d i s t r i b u t i o n d e n s i t y~ n u c l e a t e b o i l i n g , f r a c t a l t h e o r y .