Abstract: The detector system of the two-axis neutron powder diffractometer at the Heavy Water Research Reactor of China Institute of Atomic Energy was improved by increasing the number of detectors from one to four and by installing the third Soller collimators with horizontal divergence of 20′. The measurements of Fe powder diffraction patterns show that the counting rate of the diffractometer is increased by a factor of 2.3 and the resolution is also improved at the lower and mediate scattering angle region.