The quasi-peritectic reaction, which has dual characteristics of eutectic and peritectic reaction, exists in many ternary alloy systems. However, its solidification characteristics and its solidification mechanism is still unclear so far. To address this question, the Nb10Ti61Co29 alloy near the quasi-peritectic point was selected as the research object in this paper, and a series of directional solidification experiments with different growth rates (ν=1, 3, 5, 15, 30, 70 μm/s) were carried out using Bridgman directional solidification technique. Then the solidification structure at each growth rate was analyzed by XRD, SEM and EDS, and the microstructure evolution law of these directionally solidified samples was clarified. The results show that, the solidification structure of this alloy at different growth rates includes initial transition zone, steady-state growth zone and quenching zone. As the growth rate increases, the profile of the initial growth interface in the initial transition zone becomes more and more clear. With these changes, the relationship between the steady-state growth region and the initial transition region becomes smaller. Moreover, the quenching interfaces go through the transition from flat-bound to cell-oriented to dendrite in turn with the increase of the growth rate. In especial, the quenching interface is flat when the growth rate is 1 μm/s, whereas the quenching interface is roughly cellular when the growth rates are 3 and/or 5 μm/s. Lastly, the following four solidification reactions will occur successively in the process of equilibrium solidification, which was calculated by CALPHAD method, (a) L→α-Nb; (b) binary eutectic reaction L→α-Nb + TiCo;α-Nb TiCo; (c) ternary quasiperitecticcoated reaction L+TiCo→α-Nb +Ti2Co and (d) binary eutectic reaction L→α-Nb + Ti2Co.