The present invention provides an application of an SP peptide or a derivative thereof in preparing medicines for preventing or treating asthma. The peptide or the derivative thereof is the SP peptide shown in Formula I or a pharmaceutically acceptable salt or ester thereof. The present invention also provides a method for treating asthma, the method comprises: administering to a patient with medicine containing the peptide or the derivative thereof with an effective therapeutic dosage. It proves through researches of the present invention that, the peptide or the derivative thereof can effectively alleviate pathological symptoms of asthma, especially pathological symptoms of allergic asthma. In the formula (I), Xaa1 is deletion, Ala, Gly, Val, Leu or Ile; Xaa2 is Thr or Ser; Xaa3 is Tyr, Phe or Trp; and Xaa4 is deletion, Ala, Gly, Val, Leu, Ile or Pro. Xaa1-Gln-Xaa2-Xaa3-Thr-Ser-Gly-Xaa4  (Formula I)