A new hourly rainfall dataset is formed using variational method, based on raingauge and radar-retrieved rainfall intensity. The new data are used to investigate temporal and spatial variations of precipitation structure within 111-km radius centered the typhoon, especially the evolution of rainfall structure during the concentric eyewalls cycle before Saomai landfall. The authors find that typhoon Saomai had concentric eyewalls before it landed, and the mean radii of the inner and outer eyewalls were 24 km and 59 km, respectively. The radius of the outer eyewall did not minish due to the rapid landfall of typhoon Saomai after the concentric eyewalls combination. During concentric eyewalls circulation, the precipitation in the inner and outer eyewalls and rainband regions was very heavy. In the outer eyewall region, the time series of mean rainfall rate was more variable than that in the inner eyewall and rainband regions. And in the inner and outer eyewalls regions, the mean rainfall rate increased with time, but in the rainband region it decreased. The precipitation in the inner-core and outer regions was also heavy, and the mean rainfall rate in the inner-core region increased abruptly about the three hours before Saomai landed, and then it decreased, accompanied with the reduction of the typhoon intensity after Saomai landed. The distribution of precipitation of typhoon Saomai was asymmetric. Before Saomai landfall, the maximum rainfall rates in the inner eyewall, outer eyewall, and rainband regions occurred in the right quadrant relative to the storm moving track, and the azimuth in the rainband region was always to the right of those in the inner and outer eyewalls regions. The azimuth of the maximum precipitation in outer eyewall and rainband regions varied with time during the concentric circulation. After typhoon Saomai landfall more precipitation in the inner-core and outer regions appeared in the back quadrant relative to the storm track.