The copolymer of poly (1, 4-phenylene sulfide-2, 4-phenylene sulfide acid)[p-PPS-m-PPSA] and its nano HA composite [NHA/ p-PPS-m-PPSA] were recently developed as a new kind of inorganic-organic system for biomaterials. This kind of copolymer and its nano-HA composites may have a potential use in loaded bone substitutes, fixation or tissue engineering. In the present research the in vitro behavior of this kind of composites has been investigated in the SBF, and the surface changes were measured by XRD, XPS. SEM and EDS. The results showed that the copolymer and the NHA/ p-PPS-m-PPSA composites were very stable in SBF. The Ca, P content increased to 1.64wt% and 0.77wt% on the surface of p-PPS-m-PPSA, and the Ca/P was 1.63, near to that of the stoichiometric HA, 1.67 meanwhile the Ca, P content increased on NHA/ p-PPS-m-PPSA surface increased to 8.50wt% and 3.42wt% and the Ca/P ratio of surface of the NHA/ p-PPS-m-PPSA composites decreased slowly from 2.01to 1.83 during the incubation in SBF. Analysis demonstrated that the precipitate on copolymer of p-PPS-m-PPSA was HA and the precipitate on the NHA/ p-PPS-m-PPSA surface was HA, TCP and carbonated-apatite. All results showed that both the copolymer of p-PPS-m-PPSA and NHA/ p-PPS-m-PPSA composite were stable and bioactive, and might have a promising potential use in implantation and tissue engineering.