Considering the challenge that the parameter of inductor is fixed and its adjustment is difficult in traditional power electronic circuit, herein we present a newly structural transformer with adjustable leakage inductance which integrates transformer and inductor. Its leakage inductance can be adjusted online. Secondary winding of the newly structure transformer is connected in series with the inductance winding and the leakage inductance can be changed by adjusting the contact area of the transformer core and the inductor core. The structure and principle of the transformer with adjustable leakage inductance are introduced. A newly structure transformer is designed using equivalent magnetic circuit method. The transformer with leakage inductance adjustable are modeled and simulated by finite element simulation software Ansoft Maxwell. The variation of inductor inductance with the core contact area and the electromagnetic properties of the new transformer with leakage inductance adjustable are shown in this thesis. Finally, the transformer with leakage inductance adjustable is manufactured, and the experimental platform is built. The results show that the principle of the transformer with leakage inductance adjustable is reasonable and its design is feasible.