As critical-dimension (CD) shrink below 0.18um, CD control becomes a major concern. Normally there are four approaches to improve CD control: to improve intra-field, intra-wafer, inter-wafer and inter-lot CD uniformity. In this paper, we propose a simple method to improve intra-wafer CD uniformity by optimize developing recipe. In DUV photolithography, intra-wafer CD variation is the major contributor to the overall CD variations. However there are many factors that may impact intra-wafer CD uniformity: Photoresist thickness uniformity, PEB uniformity, wafer surface roughness, substrate reflectivity and developing uniformity, so the situation become very complicated. In our studies, we tried to focus mainly on the developing uniformity of DUV process. To isolate the impact of developing method from other process factors, we proposed a simple method to check developing rate (Rmin) uniformity by photoresist thickness measurement. With this method, we had save a lot of time and manpower in developing recipe tuning and also had a deeper understanding of developing process of DUV resist.