A meta-analysis was performed based on the discovery of olfactory training improving the olfactory ability. The samples include health elders and the patients of Parkinson disease, olfactory diseases, postinfectious olfactory loss, and posttraumatic olfactory loss. The result shows a positive and statistically significant effect of olfactory training in the case of all olfactory abilities. Interestingly, a difference was observed between effectiveness of olfactory training for threshold and other evaluated criteria. A reasonable explanation is that identification and discrimination are dependent on individuals' cognitive abilities, while threshold is more related to peripheral olfactory system.