Preparing method for light and high-strength square pipe

The invention discloses a preparing method for a light and high-strength square pipe. The method includes the following steps that after a square pipe die is cleaned, a releasing agent is sprayed to the surface of a core die of the square pipe die; secondly, formula glue is prepared; thirdly, carbon fibers and a foam layer are sequentially laid on the surface of the square pipe die obtained afterspraying of the releasing agent, then winding of the carbon fibers is conducted, and an inner interlayer is obtained; fourthly, carbon cloth is rolled and wrapped on the surface, not forming a foam layer, of the interior of the inner interlayer till the carbon cloth is flush with the foam layer, and a combined part is obtained; and fifthly, the carbon fibers are wound around the surface of the combined part, then high-temperature curing is conducted, die releasing is conducted after cooling, and a square pipe is obtained. By means of the preparing method, the foam layer is led in the carbon fiber laying process for pr