The invention relates to a pet food supplementing trace elements for dogs and a preparing method thereof. The pet food comprises following components by weight: 3-10 parts of magnesium sulfate, 1-2 parts of ferrous sulphate, 0.1-0.5 part of copper sulphate, 0.05-0.3 part of manganese sulfate, 1-4 parts of zinc sulfate, 0.2-0.8 part of calcium iodate, 0.1-0.3 part of sodium selenite, 20-50 parts of starch, 30-70 parts of cane sugar, 1-5 parts of a flavoring agent, and 3-7 parts of pig bone meal. The pet food supplements the trace element components which domestic dogs lack, improves absorption of the trace elements, and is characterized by good taste, high bioavailability, simple production equipment, easy operation and low cost. The pet food overcomes the disadvantages of common trace element preparations used for dogs, namely inadequacy absorption, bad taste, and the like. According to the pet food and the preparing method thereof, a manner of producing the dog food supplementing the trace elements by utilization of a common pet food production puffing technology in China is developed, is a major breakthrough for the pet food processing technology in China, makes up for blanks in the pet market in China, and takes the lead in the pet food processing technologies in Tianjin and surrounding areas.