An LED backlight driving circuit including a boost circuit and a transformer current balance circuit is provided. The boost circuit provides a total current for n LED strings, and the transformer current balance circuit is coupled to the LED strings and includes n−1 transformers. A first LED current-balance-circuit (CBC) includes a switching-transistor connected to a secondary-winding of a first-transformer, and an nth LED CBC includes a switching-transistor connected to a primary-winding of an (n−1)th transformer. An ith (1 2) LED CBC includes a switching-transistor sequentially connected to a primary-winding of an (i−1)th transformer and a secondary-winding of an ith transformer. The passive-transformers are applied in the LED driving circuit to implement current balance/equalization, such that the LED backlight driving circuit is suitable for a system with any odd or even number (greater than 1) of the LED strings connected in parallel, so as to reduce the cost of the system.