The invention belongs to the field of drilling fluid additives, and particularly relates to an emulsion microsphere blocking agent for drilling fluid and a preparation method of the emulsion microsphere blocking agent. The emulsion microsphere blocking agent comprises the following components in parts by weight in a manner of inverse emulsion polymerization: 70-90 parts of white oil, 5-10 parts of polyglycerol monostearate, 0.5-2 parts of polyoxyethylene dehydrated sorbitol polyoxyethylene sorbitan monooleate, 50-70 parts of N,N-dimethyl acrylamide, 100-130 parts of distilled water, 10-15 parts of sodium carbonate, 15-25 parts of crylic acid, 2-7 parts of vinyl trimethoxyl silane, 0.2-0.5 part of a complexing agent, 0.5-1.5 parts of an initiator and 0.02-0.05 part of a chain terminating agent. A prepared product is of a micro nano core-shell structure, is capable of effectively blocking micro cracks of different grades, is good in blocking de-filtration effect and has a lubrication effect which can be compared with that of a lubricant.