Abstract: Femtosecond laser pulses induce intriguing transient photochemical reactions with semiconductors at the sample surface, due to its ultrashort duration and ultrahigh peak power. Taking advantage of these characteristics, material can be effectively doped. The doping level is likely far beyond the solid solubility limit (so called supersaturated doping), meanwhile quasi-periodic structures with micro/nano-scales are created at the material surface as well. As a result, surface properties are strikingly changed, e.g. ultra-high absorption over a broad range from near ultraviolet to infrared emerges, which breaks the limit of traditional physics and brings novel applications. In this review, we summarize the basic theories and several physical models of femtosecond laser-silicon interaction, introduce its applications in relevant areas, and depict future prospects of femtosecond laser hyperdoped and processed silicon.