NOVELTY - Preparing attapulgite solid comprises: (A) purifying attapulgite, mixing with deionized water, stirring, filtering and screening; (B) taking purified attapulgite into sulfuric acid-water solution, stirring, filtering, washing filter cake and screening; (C) taking silane coupling agent into aqueous solution, reacting and stirring, filtering, drying and screening; and (D) taking potassium hydroxide with deionized water, dipping silane coupling agent, controlling temperature, impregnating, standing and aging, filtering, crushing and sieving to obtain attapulgite solid.    USE - Method of preparing attapulgite solid used for synthesizing biodiesel.    ADVANTAGE - The method has low cost raw materials and simple preparation process.    DETAILED DESCRIPTION - Preparing attapulgite solid comprises:    (A) purifying attapulgite, mixing with deionized water, stirring with speed of 100 revolutions per minute at normal temperature, standing for 24 hours, pouring clear liquid and lower layer impurities, filtering, mashing and screening through 80 meshes sieve to obtain purified attapulgite;    (B) acid-modified attapulgite: taking purified attapulgite into sulfuric acid-water solution at normal temperature, stirring with speed of 100 revolutions per minute, standing for 24 hours, filtering, washing filter cake for neutralization, mashing and screening through 80 meshes sieve to obtain acid modified attapulgite;    (C) coupling agent modified attapulgite: taking silane coupling agent into gamma -chloropropyl triethoxysilane aqueous solution, scattering particles in acetic acid-water solution, reacting at normal temperature and stirring with speed of 100 revolutions per minute for 6 hours, standing for 3 hours, removing supernatant, filtering, washing filter, neutralizing with water, drying at 105 degrees C, mashing and screening by 80 meshes sieve to obtain silane coupling agent modified attapulgite; and    (D) attapulgite solid: taking potassium hydroxide with deionized water, dipping silane coupling agent modified attapulgite, controlling temperature at 50 degrees C, impregnating for 5 hours, standing and aging for 10 hours, filtering at 105-350 degrees C for 2 hours, crushing and sieving through 80 meshes sieve to obtain attapulgite solid.