In this paper, the minimum variance distortionless response (MVDR) beamforming technique is studied in the presence of a spatially coherently distributed (CD) source. In the first part, we propose the CD-MVDR beamforming in which the steering vector of the CD source model is used instead of the conventional point source model. We derive a theoretical expression of the white noise gain of CD-MVDR beamforming, which is inversely proportional to the square of the difference between the angular dispersion of the actual source and that of the CD-MVDR beamforming model. In the second part, based on the performance analyses, we propose an efficient optimization method for the microphone array geometry to reduce the impact of the CD source angular dispersion on the performance of the conventional MVDR beamforming. Simulation results validate our proposed theoretical expressions and show that with the proposed geometry, the conventional MVDR beamforming tends Article Title to be significantly more robust to the angular dispersion of the CD source for both white noise gain (WNG) and directivity factor (DF).