In this paper,we give out the transien t rate-equations in vertical-cavity surface-emitting lasers (VCSELs),from whi ch we obtained expressions for the decay rate and relaxation frequency,as well a s the response functions of photon and carrier for small signal modulation.Result s show that transient decay rate enhances obviously,which means the course of re laxation oscillation is shortened,when spontaneous emission factor increases.Und er the condition of small signal modulation,multiple quantum wells (QWs) with a periodic gain structure possess a much broader modulation bandwidth than general VCSELs structure. -