The invention provides a novel ultra-high-pressure flexible semi-wet process for preparing scrimber. The process comprises the following steps: material selection; sectioning; slicing; primary airingor drying; weighing and packaging; vacuum pressurization and impregnation; low-temperature heating and modification; ultra-high pressure flexible compression molding; curing; demolding; trimming; inspection; and warehousing. During ultra-high pressure flexible compression molding, a lateral oil cylinder performs primary compacting at first and stops compacting at a distance 5 mm away from a standard position; a vertical oil cylinder starts secondary compacting, and when compacting pressure reaches 500 kg/cm<2>, a pressure head stops moving, the pressure is maintained for 3-5 s, and then the pressure head returns by a distance of 3-5 mm; and the lateral oil cylinder continues compacting in place, and then the vertical oil cylinder continues compacting until a pressure is 750-1400 kg/cm<2>.The curing temperature of the curing is 90-115 DEG C. The process provided by the invention not only reduces the cost of drying, but also enhances the anti-aging performance, shear strength, fireproofperformance and density uniformity of the scrimber.