The nano-displacement measurement based on the principle of optical lever is a contactlessly measurement technology,which has been extensively used in industry and scientific research fields. In this study,with the aim to solve some intractable issues in existing optical lever apparatus,such as low resolving power,low precision,and discommodious reading device,we present a multi-amplify and data auto-collecting system with real time technology based on optical lever and position sensitive detector (PSD) sensor,and design an apparatus to measure the linear expanding coefficient. According to the multi-amplify technology,the tiny displacement is amplified significantly,meanwhile,artificial error is eliminated based PSD sensor and LabVIEW data collecting and analysis platform. The experimental measurements indicate that the system repeat precision of brassiness,iron,aluminum and red copper is 7.5,7.2,7.6 and 8.1 nm.