The future development trend of electric power grid is strong and smart grid， and information platform is strong support for the construction of smart grid. In order to make full use of computing resources， and to better satisfy the need of smart grid for reliable storage and effective management of overall information， an construction method for information platform of smart grid based on cloud computing is proposed. In addition， based on the analysis of feasibility， advantages and problems of the new method， the architecture of information platform is given. Furthermore， considering the characteristics of condition monitoring of smart grid， the cloud computing platform based on Hadoop for condition monitoring of smart grid is proposed. To implement reliable storage and fast parallel processing of massive data， such crucial problems as virtualization， distributed storage and parallel programming model of MapReduce have further been researched.