With the growing electricity supply and demand in large city, load characteristics investigation and analysis is particularly important, it is an important prerequisites for the power grid companies to do the planning. According to the historical data and the actual situation of Zhengzhou power grid, statistics for the Zhengzhou power network load characteristics index from 2007 to 2013, and then quantitative analyzes the main factors affecting the change of load characteristics of Zhengzhou power grid using the grey correlation theory , finding out the main factors affecting the change of load characteristics. This paper introduce the entropy weight method to the grey correlation analysis, it overcomes the shortcomings of traditional grey correlation calculation, the results can provide reference for the planning and forecasting of power grid, etc.