The invention provides a method for improving uniformity of chemical-mechanical planarization process, comprising the steps of: forming features on a substrate; forming a first dielectric isolation layer between the features; planarizing the first dielectric isolation layer until the features are exposed, causing the first dielectric isolation layer between the features to have a recess depth; forming a second dielectric isolation layer on the features and the first dielectric isolation layer, whereby reducing the difference in height between the second dielectric isolation layer between the features and the second dielectric isolation layer on the top of the features; planarizing the second dielectric isolation layer until the features are exposed. According to the method for improving uniformity of chemical-mechanical planarization process of the invention, a dielectric isolation layer is formed again after grinding the dielectric isolation layer on the top of the features, such that the difference in height between the dielectric layer between the features and the dielectric layer on the top of the features is effectively reduced, and the recess of the features is compensated, the within-in-die uniformity is effectively improved.