The invention relates to the technical field of building materials, in particular to a self-adhesive straw ecological building board and a preparation method thereof. The preparation method comprisesthe following steps that (1) straw is collected and smashed for standby application; (2) an alkaline solution is fed into straw powder, then a filtering net is used for pressing to make the straw powder be soaked in the alkaline solution for thermal plasticization, and standing is conducted for 40-60 min; (3) quartz powder is added to a mixture in the step (2), and the new mixture is stirred evenly and heated to be in a gel mode; (4) the gel-like mixture is spread in a die, and a building board is formed through pre-pressing and hot-pressing; and (5) the building board is subjected to vacuum drying at the lower temperature until the moisture content is lower than 2%, and the finished building board is obtained. According to the building board provided by the invention, the straw to be recycled is sufficiently utilized, consumption of pure wood is avoided, the environment is protected, and meanwhile the problem of pollution to the environment caused by application of adhesives containing harmful substances or high cost caused by application of pollution-free adhesives is avoided.