The invention relates to a method for detecting amaranthus palmeri in plants and plant products through the PCR technology, and belongs to the field of detection of poisonous and harmful weeds. According to the method, specific primers of amaranthus palmeri are designed, synthesized and used for specific detection of genome DNA of amaranthus palmeri. The molecular detection method for amaranthus palmeri is fast, easy and convenient to implement, high in specificity, accurate and reliable, and the whole detection process can be completed within one workday.