Atomic ratio of 1:1 TiNi alloy powder was prepared by high energy ball milling process, then sintered by plasma in vacuum. The TiNi alloy powder and TiNi sintered sample were used to characterize the composition and microstructure by XRD, EDS and SEM, the hardness of the sintered sample was tested. The experimental results show that the TiNi powder was amorphous form after 22h high energy ball milling, the solid state reactions obviously take place and the new phases,such as TiNi, ,Ti3Ni4 ,appear after 30h high energy ball milling. phases of the sintered sample phase are TiNi, Ni4Ti3,Ni3Ti and Ti2Ni, its microstructure is mainly composed of fine grain with size of less 2 micron, its average Vickers hardness is up to 900Hv, after one year natural aging, its average Vickers hardness is down to 680Hv. The hardness of TiNi alloy prepared by plasma sintering is 2 ~ 5 times of that prepared by arc melting method.