The invention discloses a light seedling raising medium and a manufacturing method. The main ingredients of the light seedling raising medium comprises 10 to 60 mass percent of biomass power plant ash, 0 to 30 mass percent of grass carbon, 0 to 30 mass percent of organic fertilizer, 0 to 30 mass percent of rice hull or straw and 5 to 20 percent of vermiculite. The ingredients are mixed and used as a base material and each kilogram of the base material is added with 5 to 10 grams of urea or fertilizer. The biomass power plant ash is modified by a PH regulator till the PH value is 5 to 6.5, and the power plant ash, grass carbon, organic fertilizer and straw are mixed in a ratio, stirred, sterilized and fermented to obtain the light seedling raising medium. The medium is low in price, rich in nutrients, simple and convenient in operation and suitable for the industrial seedling raising of forest wood such as robiniapseudoacacia, alder, liquidambar formosana hance, aleurites fordii and camellia oleifera abel.