We　adopted　a　topological　optimization　theory　to　solve　issues　involving　balance　weights　in　pitching　platforms　of　laser　tracing　measurement　systems,　which　cannot　reach　required　masses　in　a　finite　volume.　This　theory　was　used　to　optimize　the　lightweight　mechanical　structure　of　connecting　plates　and　the　lifting　frames　of　pitching　platforms.　Stress　analysis　was　performed　on　a　model　that　was　reconstructed　via　topology　optimization　using　code　from　reference　[17].　Simulation　results　showed　that　the　weight　of　the　optimized　mechanical　structure　of　the　pitching　platform　was　reduced　by　1.65　kg,　with　a　weight　reduction　of　55.7%.　After　optimization,　the　weight　of　the　pitch　frame　was　reduced　by　0.628　kg,　with　a　weight　reduction　of　27.9%,　and　the　weight　of　the　counterweight　was　reduced　from　7.8　kg　to　4.6　kg　using　the　same　volume　and　material.　This　proposed　method　effectively　solves　the　contradiction　between　the　volume　and　mass　of　the　counterweight　toward　a　lightweight　mechanical　structure　in　laser　tracking　measurement　systems.　Copyright　©2022　Journal　of　Harbin　Engineering　University.