Disclosed are a pyrazole compound or a salt thereof, a preparation method therefor, a herbicidal composition and use thereof. The pyrazole compound or a salt thereof has a structure as shown in formula (I): wherein, R represents wherein, R', R", and R'" represent hydrogen, C1-C4 alkyl, C1-C4 halogenated alkyl, C1-C4 alkoxy or halogen, R', R", and R'" may be the same or different； R 1 represents C1-C3 alkyl； R 2 represents hydrogen or C1-C4 alkyl； R 3 represents hydrogen or C1-C6 alkyl, optionally substituted phenyl, optionally substituted pyridyl, optionally substituted alkenyl, optionally substituted alkynyl, C1-C6 alkyl carbonyl, C1-C6 alkoxyl carbonyl, C1-C6 alkyl carbonyl methyl, etc. A compound having a pyrazole structure not only has excellent herbicidal effect on barnyard grass, but also is safe to rice in post-emergence application. More surprisingly, it also has good control efficacy on barnyard grass resistant to major herbicides, such as penoxsulam, quinclorac, cyhalofop-butyl, propanil, etc.
