The invention provides a universal serial bus interface device and a method thereof, the device is connected between a host side and an equipment side, the device comprises a data transmission converting unit, a control signal generating unit, a protocol delaying unit and a clock generating unit, wherein the data transmission converting unit is used to receive a data signal which is input by a first UTMI interface, and then the data signal generates a data signal which can be received by a second UTMI interface through a digital circuit basing on a UTMI interface protocol, the control signal generating unit is used to receive a control signal which is input by the first UTMI interface, and the control signal generates a control signal which can be received by the second UTMI interface through the digital circuit basing on the UTMI interface protocol, the protocol delaying unit performs protocol delaying to the converted signals according to parameters needed by simulation, the clock generating unit is used to generate clocks supplying for the first UTMI interface, the data transmission converting unit, the control signal generating unit and the second UTMI interface.