Disclosed is a substituted pyrimidine compound having a structure as represented by formula PY. See the description for the definition of each substituent in the formula. The compound of the present invention provides broad-spectrum bactericidal, pesticidal, and acaricidal activities, provides great control effects against plant diseases such as cucumber downy mildew, corn rust, wheat powdery mildew, rice blast, and cucumber gray mold, specifically provides improved control effects against cucumber downy mildew, corn rust, wheat powdery mildew, and rice blast, provides great control effects against aphid, carmine spider mite, diamondback moth, and armyworm, and acquires great effects at a minimal dosage. The compound of the present invention also provides characteristics such as a simplified preparation method.