Mg/Ti bimetal composites were fabricated by ultrasonic-assisted solid-liquid compound casting with an additively manufactured Ti-based pyramidal lattice structure at the interface. The Taguchi method was carried out to optimize the lattice parameters. The optimized geometric parameters include: the strut diameter (d) is 1 mm, the ratio of strut length to diameter (l/d) is 3, and the ratios of the upper and lower node to diameter (d₁/d and d₂/d) are 2.5 and 2.5, respectively. The ratio of strut length to diameter is the most significant factor affecting failure strength. The failure strength of the Mg/Ti bimetal joint with the optimized lattice structure is 77.3 MPa. Experimental and simulated results show that the failure strength increases first and then decreases with the increase of l/d, and it reaches the peak value when l/d is 3.