The optical observations of the relationship between emerging magnetic fluxes and flares are reviewed and the characteristics essential to the flare-productive emerging flux regions are studied. Examining several essential parameters, i.e. location of emergence, orientation of bipolar axis, growth rate and magnetic shear development, we conclude that the emergence of twisted magnetic flux ropes is the most important factor for the major flare activities. Some observational evidence of the emergence of the twisted magnetic flux ropes is demonstrated with high resolution Hα pictures.