TOMSPLOT Software Package is a software tool developed from IDL which is used for image processing and data analysis as well as data calculation of volcanic cloud obtained from NASA TOMS satellite data. TOMSPLOT is now a GUI interface (widget) based software tool. Details of how to use it can be found at TOMSPLOT tutorial. Generally Speaking, it uses NASA TOMS Level-2 data product as the input file. Through the TOMSPLOT tool, the volcanic cloud area can be verified and the SO2 pixel values within the volcanic cloud area can be reprocessed with the SO2 calibrated algorithm (Kerr-Kruger algorithm). The total tonnage SO2 amount of the whole volcanic cloud area can be calculated. The aerosol index image can also be displayed. The scale, color, area and other image display parameters of the image can be adjusted and redisplayed.