Abstract: In this paper, the authors studied the preparation and the mechanism of producing pores on tiny porous HAp based biomaterial.At first, the multiplex powder was moulded by cold pressing and isostatic pressing; then, the samples were sintered at 1200℃ for about 3h in air and the tiny porous HAp-ZrO2 composites with different pores were obtained. When the moulding pressure, sintering temperature and keeping temperature time are all the same, the flexural strength of the composite is becoming lower with the increase of additive and nano-zirconia contents. But the lowest value of flexural strength is still about 23MPa which is much higher than that of the porous hydroxyapatite in literatures. The added quantity of additive and nano-zirconia is the key factor which influences the diameter and ratio of pores in the composite. Other factors, such as moulding mode, sintering temperature and the time of keeping temperature, can influence them too.