The invention relates to a preparation method of an adsorbent for purifying hydrogen sulfide, hydrogen phosphide and arsenic hydride simultaneously, and belongs to the technical field of adsorbent preparation. The method comprises the steps that P123 or F127 is dissolved in a dilute acid solution and stirred till being dissolved, a certain number of pore-enlarging agents are added, stirring and even mixing are carried out, ethyl orthosilicate is added, the mixture is poured into a reaction kettle after being stirred for 1-6 h, powder obtained after crystallization is washed with distilled water till the color of test paper is not changed, the dry powder obtained after drying is placed into a roaster to be roasted, temperature is naturally decreased to indoor temperature, an adsorbent carrier is obtained, the obtained carrier is dissolved in water, a certain amount of metal salt is added, filtering, drying and roasting are carried out, and then the large-aperture adsorbent is obtained. The preparation method is easy to implement, the metal salt impregnant is low in cost and easy to obtain, the desorption effect is good even at low temperature, and a wide development prospect is provided for simultaneous desulfurization, dephosphorization and dearsenization through a dry method.