The invention relates to a method for preparing a 5A molecular sieve for straight-chain paraffin adsorption through adopting attapulgite, and belongs to the technical field of molecular sieve adsorbents. The method comprises the following steps: 1, calcining attapulgite at a high temperature, and immersing in a hydrochloric acid solution; 2, fully dissolving attapulgite in an aqueous solution of sodium hydroxide; 3, fully dissolving sodium hydroxide and sodium metaaluminate in water; 4, rapidly mixing a solution obtained in step 2 with a solution obtained in step 3, violently stirring to obtain a milky colloid, crystallizing the colloid at 80-95DEG C for 4-6h, cooling, filtering, washing until the pH value is less than 9, and drying to obtain raw powder of a 4A molecular sieve; and 5, carrying out ion exchange of the raw powder of a 4A molecular sieve and a calcium chloride solution to obtain the 5A molecular sieve. The static saturated adsorption capacities of the 5A molecular sieve to n-decane and n-pentadecane reach 0.0716g/g and 0.123g/g respectively. The method for preparing the 5A molecular sieve through adopting a cheap and easily available attapulgite resource is used to substitute a traditional chemical raw material method, and the 5A molecular sieve has a good saturated adsorption capability to straight-chain paraffin.