A digital polarization agile monopulse de- tector was presented. Detection work°ow, method of virtual polarization synthesizing and method of digital monopulse angle error extraction based on variable polar- ization antenna with linearly polarized subarrays were pro- posed. Polarization agile was realized by utilizing digital controlled phase shifters in multichannel T/R module. The gain of antenna array can be improved and the beamwidth of cross polarization less than ¡15dB can be widened by ap- propriately increasing the number of subarray. The mea- sured results show the availability of the detector and the e®ectiveness of virtual polarization synthesizing and digital monopulse angle error extraction method.