The invention belongs to the field of pharmaceutical preparations, and particularly relates to an octreotide acetate lyophilized powder injection and a preparation method thereof. The octreotide acetate lyophilized powder injection includes carboxymethyl chitosan and hydroxypropyl-beta-cyclodextrin, and a pH buffering agent is acetic acid and glycinamide. The carboxymethyl chitosan can inhibit thegrowth of bacteria in a product; hydroxypropyl-beta-cyclodextrin can improve the resolubility of the product, and can play the role of a lyophilization protectant together with mannitol to improve the stability of the product; In addition, the carboxymethyl chitosan and hydroxypropyl-beta-cyclodextrin can form a weak gel in a solution, which plays a role in sustained release of octreotide acetate. The octreotide acetate lyophilized powder obtained by the invention has low bacteria and impurities content, and the stability and resolubility are also superior to that of the traditional products.