This paper designs a miniaturized ultra-wideband Balun filter based on the low-temperature co-fired ceramic (LTCC) technology. The Balun filter consists of a fifth-order bandpass filter and a Marchand Barron-based modified Barron cascade. The bandpass filter is designed as a wideband high rejection Barron filter using a coupled resonant design method, and an innovative inductive cascade topology is used between the second, third and fourth order resonance, thus the relative bandwidth of 48% or even wider has been realized. The coupling between the Balun input and output uses a parallel stacked coupling spiral transmission line, which greatly enhances the coupling between transmission lines and widens the bandwidth of the Balun. The Balun filter passband is 1.71~2.76 GHz,and the insertion loss is less than 2.3 dB.At 50~669 MHz, the rejection is greater than 35 dB,at 669~1 245 MHz, the rejection is greater than 17 dB,at 3 205~3 400 MHz, the rejection is greater than 27 dB,and at 3 400~6 000 MHz, the rejection is greater than 30 dB. The phase difference and amplitude difference of the signals of the two output ports are 180°±15°(1 710~2 340 MHz), 180°±10°(2 500~2 760 MHz) and ±1.0 dB, respectively. The proposed filter has high versatility and good market application prospects.