The Reactor Experiment for Neutrino Oscillation (RENO) started data-taking from August, 2011 and has successfully measured the smallest neutrino mixing angle θ_13 by observing the disappearance of reactor electron antineutrinos. Electron antineutrinos from the six reactors at Hanbit Nuclear Power Plant in Korea are detected and compared by the two identical near-and-far detectors. In 2016, RENO has published an updated value of θ_13 and its first measurement of dm^2_ee based on energy dependent disappearance probability. RENO has made efforts to reduce systematic uncertainties based on a careful understanding of backgrounds and analysis methodology. The measured prompt spectra show an excess of reactor electron antineutrinos around 5 MeV relative to the prediction from common reactor models. In this talk, we present a precise measurement of θ_13 and dm^2_ee using more data and improved systematic uncertainties.