The difficulties of 1~18 GHz ultrawideband one subtwo power divider were analyzed.The Wilkinson power divider with two different structures were designed in this paper.The power divider with better performance was chosen and fabricated based on the results of cosimulation of ADS and HFSS.The test results of the 1~18 GHz ultrawideband one subtwo power divider showed that,from the frequency of 1~18 GHz,the port return loss was less than -15 dB,the isolation of the two ports was more than 20 dB.The proposed power divider can be used for the ultra wide band system.