In this paper, an ultra-wideband stripline 3dB orthogonal directional coupler based on LTCC is studied. The operating frequency is 0.5–3.5GHz and the relative bandwidth is 150%. The difficulty lies in the requirements of ultra-wideband, high performance and miniaturization. In this paper, we started from the design and manufacture of the product, combined with the theoretical basis, through the HFSS simulation software to complete the entire design. In the design process, because the required bandwidth is very wide, the final decision to use one and five coupling units' cross-cascaded structure, both to ensure high performance and ensure the size of the miniaturization. The final design results, the working bandwidth is 0.5–3.5GHz, insertion loss ≤ 4.5dB, isolation greater than 18dB, VSWR less than ≤ 1.35, the phase difference ≤ ± 3 °, the final size of the design model is 12.7mm ∗ 7.5mm ∗ 2.3mm.