A pseudoline source is realized by using an accelerator-based deuterium-tritium point-neutron source. The pseudoline source is obtained by time averaging of the continuously moving point source or by superposition of the finely distributed point sources. The line source is utilized for fusion blanket neutronics experiments with an annular geometry to simulate a part of a tokamak reactor. The source neutron characteristics are measured for two operational modes for the line source: the continuous and the stepwise modes, with activation foil and NE-213 detectors, respectively. The neutron source characteristic is calculated by a Monte Carlo code to give a source condition for a successive calculational analysis of the annular blanket experiment. The reliability of the Monte Carlo calculation is confirmed by comparison with the measured source characteristics.