More and more applications have been made to realize lightweight design of aerospace parts by additive manufacturing to form complex lattice structures. However, the lattice structure design and its performance evaluation are still lacking. In this study, the diamond structure was used as the matrix, and the specimens with different geometric parameters were designed for forming with TC4 titanium alloy, aiming at lattice density and structure form. Compression tests were carried out on the formed specimens to study the differences of compressive properties between specimens of different sizes. The results show that the stress of the diamond lattice structure specimens will concentrate at the joint position and cause fracture after being loaded. Increasing cell density can alleviate the phenomenon of stress concentration, increase specific strength, reduce cell size and add shell can make the stress uniform and improve the stability. Small cell size specimens are more sensitive to metallurgical defects such as spheroidization and pore, resulting in a decrease in strength.