The invention provides a method for obtaining compact global feature descriptors of an image and an image retrieval method. The method for obtaining the compact global feature descriptors of the image comprises the following steps: obtaining at least a local feature descriptor of the image; selecting one or more local feature descriptors from all the local feature descriptors; carrying on dimensionality reduction to the selected local feature descriptors; obtaining the local feature descriptors after dimensionality reduction; converting the local feature descriptors after dimensionality reduction into global feature descriptors for expressing visual feature of the image according to a first rule; carrying on data compression to the global feature descriptors; and obtaining the compact global feature descriptors of the image, wherein byte size of the global feature descriptors can be varied according to the variation of parameter values in the first rule. Through the adoption of the method, the obtained global feature descriptors are more compact and have scalability, and the defect that a mobile terminal with lower internal memory has insufficient space in the prior art can be solved.