Flow characteristic of the desalted water influenced by three inlet structures in different diameter nomal tube, equal diameter nomal tube and tangential tube inlet of the jacketed tube in high-pressure tubular reactor was investigated based on computational fluid dynamics. The results show that the desalted water flow forms a region where the flow velocity is close to zero in the different diameter nomal tube structure and temperature of the desalted water in this region raises notablely. It is also found that the peaks of the shear stress occur at wall inside near inlet of the jacket. The other structures avoid in large extent advent of the former two phenomena and obviously reduce the shear stress value at wall. From the results, the second inlet structure is better than the third and the third better than the first.