The invention discloses a plant drought inducible synthetic promoter SP18, a plant expression vector and application of the promoter SP18 in cultivation of drought-resistant transgenic plants. The nucleotide sequence of the plant drought inducible synthetic promoter SP18 is shown in SEQ ID No.1; the nucleotide sequence shown in SEQ ID No.1 is inserted into a vector plasmid of the plant expressionvector; the identification of the situation that the promoter SP18 drives the expression of a reporter gene GUS in a soybean hairy root genetic transformation system shows that the promoter SP18 can be induced by drought stress, and the expression intensity is similar to that of a CaMV 35s promoter.