Using the TRMM TMI data and QuikSCAT surface wind data we are developing a tropical cyclone intensity estimation method. The QuikSCAT data is obtained from the Web site of Remote Sensing Systems. With a guidance of the maximum sustained wind, obtained from the QuikSCAT surface wind data, we compared it with brightness temperatures at several microwave channels, such as 19, 37 and 85 GHz. The variables are the mean TBBs, minimum TBBs for 85 GHz, maximum TBBs for 19 and 37 GHz, within 0.5, 1.0 and 1.5 degree from the TC center, or 0.5-1.0 and 1.0-1.5 degree ring. We also examined the difference temperature between the center and the eye wall. The result shows that there are several good parameters to describe the intensity. These are the mean TBB and the percentage of the area within 1.0 deg circle or 0.5-1.0 deg ring in 19 and 37 GHz.