Abstract: Based on the Kurtz theory, a measurement system of powder second-harmonic (SHG) using fiber spectrometer was designed. The test system can measure SHG in different directions by rotating the arm and not changing-direction of incident fundamental light. It has good accuracy and sensitivity. It enlarges phase-matching particles from 46m to 250m. The fundamental wavelength of 1.064m was used to measure KIO3 crystal powder SHG. The test result shows that KIO3 crystal powder has the phase-matching characteristics, which is consistent with the previous reports. The nonlinear coefficient d2 of KIO3 crystal powder obtained by simulating the experimental curve is 9.710-12m/V. The simulation value agrees with d32 of KIO3 crystal reported previously. This method is proved feasible and could be used in the study of nonlinear characteristics for other crystal materials.