Hydroxyapatite (HAP) has excellent biocompatibility and bioactivity. Synthetic HAP can be widely used as medical and eco-friendly materials. In order to know valuable information of study and development of bone tissue engineering, the influence on HAP crystals growth by the changed of fluid field and the chosen of substrates are studied. The composites materials are used as substrates, which are made of Polydimethylsiloxane (PDMS)/HAP, PDMS/bioglass, and pure bioglass, respectively, and the effect of different substrates on HAP growth are analyzed. The results show that HAP crystals growth rates are different on different substrates when the flow rate is zero. HAP crystals growth rate is highest on PDMS/HAP substrate. However, it is lowest on pure bioglass substrate. Moreover, the influence of different flow rates of HAP growth solution (Simulated Body Fluid, SBF) by a homemade flow rate adjustment apparatus is studied. Three different flow rates, 10ml/min, 15ml/min, and 30ml/min, are used in this study. Under SBF flow conditions, the sizes of HAP crystals increased and the amount of amorphous precipitate decreased.