The eigenvalue equation of the step finite strained single quantum well is deduced from Schrdinger equation, the influence of the step width on first electron energy, first hole energy, the stimulated wavelength, and the influence of the first hole energy on stimulated wavelength are studied. The results indicate that, if the In content is large, the influence of the first hole energy on the stimulated wavelength should not be neglected. The calculated value by using this model is in accord with the experiment results.