The invention discloses a method for producing light heat preservation plates by taking carboxymethyl starch as a bonding agent. In the invention, a carboxymethyl starch bonding agent and waste plant fiber powder as well as polystyrene foams are mixed to be uniform, then the mixture is placed into a mould, and moulding, demoulding and drying are carried out to obtain the plates. The plates produced in the invention have no substances harmful to human body such as methyl aldehyde and the like, and are characterized by light weight, low cost, simple production process, waste utilization and environmental protection, and the product can be widely applied to the fields of building, decoration, packaging and the like.