Electronic phase separation is one of the key features in correlated electron oxides. The coexistence and competition of multiple phases give rise to gigantic responses to tiny stimuli producing dramatic changes in magnetic, transport and other properties of these compounds. To probe the physical properties of each phase separately is crucial for a comprehensive understanding of phase separation phenomena and for designing their device functions. Here we unravel, using a unique p-n junction configuration, dynamic properties of multiple phases in manganite thin films. The multiple dielectric relaxations have been detected and their corresponding multiple phases have been identified, while the activation energies of dielectric responses from different phases were extracted separately. Their phase evolutions with changing both temperature and applied magnetic field have been demonstrated by dielectric response. These results provide a guideline for exploring the electronic phase separation phenomena in correlated electron oxides.