Microstructure architectures greatly influence the tensile properties of materials, especially for high-temperature tensile properties. A better reinforcing effect could be achieved with the same reinforcement by tailoring the reinforcement architectures. In this study, the homogeneous, linear, and network AlN were fabricated in situ by the solid–liquid reaction. The effects of different architectures were investigated on the mechanical (hardness and tensile) properties of AlN/Al composites. The AlN network presents a significant reinforcing effect in the Al matrix at room temperature (289 MPa) and 350 °C (125 MPa). The direct observation of microstructural evolution like grain orientation, grain boundaries, and strain field during the tensile deformation at 350 °C contributes to revealing the strengthening mechanism of AlN network. It is found that AlN network can strengthen grains and grain boundaries together. Besides, AlN network can impede the crack propagation and increase the crack capability of network AlN/Al composites. Our findings in this study may help design heat resistance Al materials with high performance.