The invention specifically relates to a pyrazole compound or salt thereof, and a preparation method, a herbicide composition and application thereof, belonging to the field of pesticide. The pyrazole compound or salt thereof has a structure as shown in a formula (I). In the formula (I), R is as defined in the specification, wherein R', R'' and R''' represent hydrogen atoms, C1-4 alkyl groups, C1-4 halogenated alkyl groups, C1-4 alkyloxy groups or halogen, and may be same or different; R1 represents a C1-3 alkyl group; R2 represents a hydrogen atom or a C1-4 alkyl group; and R3 is hydrogen atom, a C1-6 alkyl group, a substitutable phenyl group, a substitutable pyridyl group, a substitutable alkenyl group, a substitutable alkynyl group, a C1-6 alkylcarbonyl group, a C1-6 alkyloxycarbonyl group, a C1-6 alkylcarbonylmethyl group or the like. The pyrazole compound or salt thereof shows excellent herbicide effect on barnyard grass, is safe to paddy rice during application after seedling emergence, and more surprising, also exerts outstanding effect on barnyard grass with resistance to main barnyard grass herbicides like penoxsulam, quinclorac, cyhalofop butyl and propanil.