The KamLAND experiment searched for the oscillation of anti-neutrinos emitted from distant nuclear reactors. We observed the anti-neutrino spectral distortion, which was a piece of evidence of neutrino oscillations. Due to their clear spectral distortion, the neutrino mass difference was determined with 2.8% precision. In the near future, we will have a sensitivity also to the low energy solar neutrinos utilizing the characteristics of high light intensity. The precise measurement of low energy solar neutrinos helps us obtain a better understanding of fusion reactions. I will show the status of the anti-neutrino analysis and the purification of the liquid scintillator.