Dark energy can be studied by its influence on the expansion of the Universe. We investigate current constraints on early dark energy (EDE) achievable by the combined observational data from type Ia supernovae (557), baryon acoustic oscillations, the current cosmic microwave background and the observed Hubble pa-rameter. We find that combining these data sets provides powerful constraints on early dark energy and the best fit values of the parameters in 68% and 95% confidence-level regions are: Ωm0＝0.2897(-0.0138-0.0194)(-0.0149-0.0207),Ωe=0.0129(-0.0129-0.0129)(-0.0272+0.0381),ω0＝-1.0415(-0.109-0.1604)(+0.0891-0.1182),and h=0.6988(-0.0058-0.0081)(+0.0059+0.0083)