<p>The microchannel heat exchanger (MCHX) is a promising equipment to achieve a more efficient and compact cryogenic system, while the significant issue of axial heat conduction presents stringent requirements for its application in cryogenic environments. In order to mitigate the axial heat conduction, various structural parameters and solid thermal conductivity of the MCHX have been numerically investigated in this study. The results reveal that the efficiency of MCHX initially increases and then decreases with the increase of thermal conductivity, and peaks at a thermal conductivity (<i>λ</i>) of 10 W·m⁻¹·K⁻¹. When the <i>λ</i> exceeds 10 W·m⁻¹·K⁻¹, the axial heat conduction becomes the primary factor contributing to the efficiency of MCHX reduction and significantly strengthened by further increase of thermal conductivity. Specifically, the efficiency loss attributed to the axial heat conduction increases by 21.8% as <i>λ</i> increases from 10 W·m⁻¹·K⁻¹ to 300 W·m⁻¹·K⁻¹. Reducing the height and thickness of micro-channel ribs can effectively weaken the negative effect of axial heat conduction on the performance of MCHX under high thermal conductivity conditions. Furthermore, compared to the traditional straight ribs in micro-channels, the slotted ribs and serrated ribs prove to be more effective in inhibiting the axial heat conduction, potentially reducing the efficiency loss of the MCHX attributed to this phenomenon by nearly 50%.</p>