Abstract: In order to improve the incident neutron fluence rate at the sample position to allow both high-resolution and small sampling volume measurements, simulation and optimization on the vertical focusing monochromator, a key component of the neutron diffractometer for strain measurement to be built at China Advanced Research Reactor(CARR) was carried out using the MCSTAS code. The optimal focusing conditions, i.e. curvature radii and the tilting angle of the neighbor crystal slabs for the (511), (311) and (711) reflections under the take-off angles of 60°，90°and 120°, were obtained. A neutron fluence rate of above 10⁷ cm^－2•s^－1 at sample position, which means an intensity gain of about 6-7 relative to flat monochromator, can be achieved under these optimal conditions. To test the optimal design of the vertical focusing monochromator, (211) diffraction patterns of α-Fe sample, with no strain, tensive strain and compressive strain, respectively, were simulated. The simulated full width at half maximum of the diffraction pattern and the correspondent peak shift induced by the strain are in good accordance with the results obtained from analytical calculations. It shows that the diffractometer is at least capable of measuring the strain of above 500 με and the highest precision of strain measurement is about 20 με.