Intermediate-scale shear waves are ubiquitous in the world's ocean. They are the horizontal wavy movement along the shear interface having a typical wavelength of 100 km. Based on a simple theoretical model using the standard shallow water geophysical fluid dynamic equation, we found that these phenomena can be modeled by a kind of stable shear wave triggered by external forces, such as wind stress. Our results indicate that their amplitudes should be directly proportional to the wind stress, and the relationship between the phase speeds of the waves and their wave numbers can be expressed by a parabolic equation. Comparisons between theoretical results and data derived from the satellite IR images show good agreement.