Abstract: The present invention provides a titanium-niobium composite oxide, which includes titanium, niobium, dopant M and oxygen, and the molar ratio of the titanium, niobium and dopant M is 1:(2?x):x, and x is 0.01 to 0.2; wherein the dopant M is doped in a crystal structure with a monoclinic crystal structure formed from the titanium, niobium and oxygen, and the dopant M is at least one metal element selected from the group consisting of Sn, Al and Zr. The present invention further provides a preparation method of the titanium-niobium composite oxide, an active material and a lithium ion secondary battery using the same. The titanium-niobium composite oxide produced by the present invention has better electrical performance than the existing negative electrode materials, so that the lithium ion secondary battery using it can exhibit longer cycle life, larger electric capacity and faster charging and discharging performance, thereby having a bright prospect of the application.