The invention discloses a battery charger aiming to solve the technical problems that a charger is applicable to mobile phone batteries with different sizes and specifications and simultaneously the battery is more stable during charging and easy to operate and enhances the charging effect. The battery charger comprises an upper cover which is provided with a surface cover capable of transverselysliding along an upper surface of the upper cover; a groove for placing the battery is formed between the upper cover and the surface cover; a fixed plate is arranged inside the upper cover; the upper end of the fixed plate is connected with the surface cover; the fixed plate is provided with a spring; a pole piece button is arranged outside the upper cover; a sliding chute is arranged between the pole piece button and the upper cover; the pole piece button is connected with a positive electrode contact blade and a negative electrode contact blade through the sliding chute; and a USB spigot is arranged at one side of a lower cover and is connected with a printing circuit assembling plate. Compared with the prior art, the invention improves the installation and fixing mode of the charger on the battery, and improves the efficiency for battery charging installation operations and the charging stability as well as the service range and the value of single products.