The invention relates to a fluorescence detection method for bis (2-ethyl) hexyl phthalate based on coupling of a nucleic acid aptamer with a spherical nucleic acid. According to the invention, a variable structure nucleic acid aptamer structure is combined with a spherical nucleic acid detection platform, wherein an oligonucleotide chain used for being combined with a free foot chain of the variable structure nucleic acid aptamer is designed on the surface of a gold nanoparticle of spherical nucleic acid, and the characteristic that restriction endonuclease is cut at a specific site is utilized, so that the variable structure nucleic acid aptamer free foot chain is promoted to freely walk on the surface of the gold nanoparticle, a fluorescence signal amplification strategy is designed, the detection range of trace DEHP is expanded, and field detection is rapid and portable; and compared with the prior art for recognizing and detecting the target DEHP by adopting an antibody, the nucleic acid aptamer has the advantages that the specific recognition is better, the binding strength is higher, the preparation time of the nucleic acid aptamer is shorter than that of the antibody, the operation is simple, and the in-vitro storage is easier.