In order to overcome the shortage of load models used in transient stability analysis which cannot describe the load shedding characteristics under low voltage， some improvements on load models are proposed after studying the field measurement data and load characteristics under low voltage. New parameters are used in this new load model， including critical voltage delay time and attenuation coefficient. Both of these parameters can properly describe the load shedding characteristics in negative exponent form under low voltage conditions. In this way， the steady load differences caused by low voltage disturbances can be clearly explained while keeping the load dynamic behavior successively. The improved load model not only has better properties in describing the load dynamic characteristics during the transient stability analysis but also enhances the reliability of the simulation. The field measurement data illustrate its efficiency.