For laser-based optical fabrication, surface roughness can be reduced efficiently with laser polishing. However, it remains challenging to smooth the residual waviness and shape errors [1], [2]. Compared to continuous-wave and longer-pulse lasers, femtosecond (fs) laser processing enables high-precision material removal without inducing thermal melting. We present fs-laser-based shape correction. The material removal as a function of energy deposition was used to select sets of optimal laser parameters for high-precision figuring and smoothing glass substrates.