A precise interstellar dust extinction law is critically important to interpret observations. There are two indicators of extinction: the color excess ratio (CER) and the relative extinction. Compared to the CER, the wavelength-dependent relative extinction is more challenging to be determined. In this talk, I will present the results of our high-precision CERs and relative extinction from optical to mid-infrared (IR) bands. For the first time, we calibrate the curvature of CERs in determining CERs. The precision of our CERs is significantly improved (sigma < 0.015). With Gaia parallaxes, we calculate the relative extinction in total twenty-one bands. Our observed extinction law supports an adjustment in parameters of CCM Rv=3.1 curve together with the near-IR power law index alpha=2.07+-0.03. The relative extinction values of HST and JWST near-IR bandpasses are predicted in 2.5% precision. As the observed reddening/extinction tracks are curved, the curvature correction needs to be considered when applying extinction correction.
