Abstract: Microstructured neutron detectors (MSNDs) can achieve a tenfold increase in neutron detection efficiency over the traditional planar detectors. However, the overall detection efficiency is determined by their microstructured features. In this work, we report the influences of microstructured feature and backfilling density on the intrinsic thermal neutron detection efficiency. The design of MSND with trench patterns is optimized. The detection efficiency decreases when the trench gap is increased. The trench width can be optimized when the trench gap is fixed. The detection efficiency increases by increasing the trench depth. MSNDs having trenches with 15 m width and 5 m gap can achieve high detection efficiency and efficiency stability. With the lower level discriminator (LLD) setting at 300 keV, the detection efficiency of MSND with 15 m width, 5m gap and 200 m depth can achieve 37.77% intrinsic efficiency, which is 9.2 times higher than that of the planar semiconductor neutron detectors; The neutron to gamma-ray rejection ratio is 4.1103 for gamma rays of a 137Cs source, which is 23.7 times higher than planar ones. This work demonstrates the outstanding neutron detection efficiency and neutron to gamma-ray rejection ratio of MSNDs with trench patterns.