The invention provides a plant protective method and application of inducing immune system of plant by 4-methyl-1,2,3-thiadiazolyl-5-formic acid (NK-F001), sodium 4-methyl-1,2,3-thiadiazolyl-5-formate (NK-F002), 4-methyl-1,2,3-thiadiazolyl-5-ethyl formate (NK-F003) and methenaimde (SZG-7) to generate resistance against the plant virus. The invention also provides an application for improving the plant immunity by combination of two or three of 4-methyl-1,2,3-thiadiazolyl-5-formic acid (NK-F001), sodium 4-methyl-1,2,3-thiadiazolyl-5-formate (NK-F002), 4-methyl-1,2,3-thiadiazolyl-5-ethyl formate (NK-F003), methenaimde (SZG-7), benzthiadiazole (activated ester, BTH), tiadinil (TDL), DL-Beta-aminobutyric acid, virazole, ningnanmycin, antofine, Bingduxing No.1, Bingduxing No.2, XY-13 and XY-30 so as to induce the plant to generate antiviral activity, processing dosage forms of single and mixture preparations, and compositions and contents of effective components in the dosage forms. The invention discloses a plant inducing range and plant antiviral inducing range of compounds and compositions thereof, and application of plant protection in the fields of agriculture and horticulture thereof.