The stellar obliquity, a probe to planet migration history, is the angle between the rotation axis of the host star and the normal of the orbital plane of the planet. Various migration theories with different timescales, e.g., primordial disk misalignment (< 3 Myr), Kozai-Lidov mechanism (10^4-10^8 yr), secular chaos (10^7-10^8 yr), differ strongly in their predictions on the obliquity. These mechanisms all functions during the youth of the planetary systems (< 1Gyr). Therefore, young planetary systems are the promising targets to constrain the models and timescales of planetary formation and migration. In the presentation, we will briefly introduce measuring stellar obliquity of planets in the young systems with high-resolution spectroscopy and extreme-precise radial velocity.