A photon-counting imaging detector with a wedge-and-strip anode (WSA) can record position information on a single photon or incidence particle, so it can acquire the two-dimensional image of an objective under very low lighting conditions. In this paper, a detail description of a detector prototype built by us is firstly given, including its configuration and operating principle, then the imaging distortion of the detector is analyzed, correction methods are proposed and distortion-free images are obtained. Resolution tests are taken using a USAF1951 resolution target placed in front of the detector. The detected image shows that the 6th element in the 2nd group of the USAF1951 target can be differentiated by the naked eye. Finally, in order to remove the subjectivity error produced by human eye observation and to ensure measurement accuracy, the imaging modulation index is computed. The computed results show that, for the 6th element in the 2nd group of the USAF1951, its imaging modulation index can reach 57% and 37% in the vertical and horizontal, respectively. This result indicates that proposed detector prototype can differentiate the strips above absolutely with a 7.13 lp/mm, i.e., the spatial resolution reaches 0.14 mm.