The invention belongs to the field of biotechnology and provides a plant-derived SAC3 (Strong Activation Domain from China Fir-3) and application thereof. The plant-derived SAC3 has an amino acid sequence of DEEGCGTCFDFAENTEQKEFLDNWHFEDDFVDYAQFAVFDDTADSAWDVVNLEAFIDGDYSTSWELETIC; the SAC3 is separated from a cDNA library of cunninghamia lanceolata; CPRG results show that the activation function is about 19 times as high as that of VP16 in the yeast; Gal4-UAS-based double-luciferase system results show that the activation activity of SAC3 in Arabidopsis thaliana is more than twice as high as that of VP16 and is 50 times as high as that of EDLL. The SAC3 can be applied to the genetic engineering technology of plants, so as to accurately activate the expression of specific genes in the plants, improve the important characters associated with the specific genes, and greatly enhance the economic value of crops.