Nanoscale La-doped PbTiO₃(PLT)\TiO₂ (PLTT) composite structures have been fabricated. It shows that the structure presents reliable resistive switching (RS) behavior, and importantly, has great tunability on RS characteristics such as forming/set/reset voltages and resistance ratio by adjusting the PLT layer thickness. Particularly, the set voltage can be tuned at a large range from several volts to dozens of volts. Meanwhile, the set current keeps almost the same, indicating the RS is current dominating. The space-charge-limited current (SCLC) feature indicates that the localized traps are decisive for the RS. Our result sheds light on the prospects of composite structures for designing tunable RS devices.