The invention relates to foam concrete prepared from kitchen waste and construction waste as raw materials and a preparation method thereof. The preparation method includes following steps: collectedkitchen waste is subjected to impurity removal and oil removal treatment, then water is added for grinding to prepare slurry, then bacteria are introduced into the slurry for fermentation; after fermentation is completed, a foam stabilizer is added for physical foaming; finally, obtained foam is evenly mixed with recycled construction waste, cement and other concrete raw materials, and injection molding, curing and demolding are conducted. According to the invention, the synchronous coordination treatment of the construction waste and the kitchen waste is achieved, the manufacturing cost of the foam concrete is saved, the treatment cost of the kitchen waste is reduced, and the concepts of turning waste into wealth and recycling waste and waste are fully realized.