The invention relates to an African agapanthus auxin response factor ApARF2 and an encoding gene and probe thereof. Protein is shown in a or b, wherein a is protein formed by an amino acid sequence shown in SEQ ID NO.4, and b is protein which is formed by substitution or deletion or addition of one or more amino acids to the amino acid sequence shown in SEQ ID NO.4, has African agapanthus ApARF2 protein activity and is derived from a. The invention further provides a nucleotide sequence for encoding the protein and the probe for detecting the nucleotide sequence. An African agapanthus auxin signal transduction pathway is adjusted and controlled through the gene engineering technology, the purposes of controlling growth and development of African agapanthus and establishing organ morphology are achieved accordingly, a theoretical basis is provided for molecular breeding, and high application value is achieved.