An organic light-emitting diode (OLED) display panel and a manufacturing method thereof are disclosed. The manufacturing method includes: providing a first substrate (1) and a second substrate (2), in which the first substrate (1) is provided with an OLED layer (3); coating a first sealant (4) on a surface of the OLED layer (3) of the first substrate (1); coating a second sealant (5) on a surface of the second substrate (2) and coating a third sealant (6) outside the second sealant (2) on the second substrate (2), in which the first sealant (4) has a viscosity less than that of the second sealant (5); and pressing the first substrate (1) and the second substrate (2) together and performing curing to allow the second sealant (5) to cover the first sealant(4) and fill a gap among the first substrate (1), the second substrate (2) and the third sealant (6). The manufacturing method can reduce the tension of a contact surface between the sealant and an OLED in the curing process, reduce the damage to the OLED, and ensure that a sealing structure of the OLED has good water resistance.