Moisture adsorption of brown rice is the fundamental reason for kernel cracking, which restricts the quality and texture of germinated brown rice. Moisture adding technique needs to be further optimized to reduce cracked kernel percentage of brown rice before germination. The whole moisture adding interval was divided into 12 intervals of 13.0%~14.4%,14.4%~15.5%,15.5%~16.5%,16.5%~17.8%,17.8%~19.2%,19.2%~20.9%,20.9%~22.2%,22.2%~23.2%,23.2%~24.3%,24.3%~25.6%,25.6%~27.3% and 27.3%~29.0%, and moisture adding procedure was finished within 1.0min,1.5min,2.0min,2.5min,3.0min,3.5min,4.0min,4.5min,5.0min and 5.5min respectively. In each interval, cracked kernel additional percentage was found to first decrease and then increase in range of moisture adding percentage. Mathematical models to describe variation in cracked kernel additional percentage were established, and derivation to models was applied to determine the optimal moisture adding rate. Optimal moisture adding rates for brown rice with moisture of 13.0%,14.4%,15.5%,16.5%,17.8%,19.2%,20.9%,22.2%,23.2%,24.3%,25.6% and 27.3% were 0.3212%/min,0.2851%/min,0.4338%/min,0.3299%/min,0.3485%/min,0.4382%/min,0.4993%/min,0.5494%/min,0.6396%/min,0.7352%/min,0.8735%/min and 0.8436%/min, which varied first slowly, then rapidly and finally slowly within the whole moisture adding interval. Based on above values, the mathematical model to describe moisture adding rate within the whole moisture adding interval was obtained. Compared with traditional segmented moisture adding technique, optimized moisture adding technique resulted in decreases of (41.48±0.15)% and (43.67±0.26)% in the cracked kernel additional percentage of non-germinated and germinated brown rice, respectively, while the germination rate and γ-aminobutyric acid content of germinated brown rice had increases of (6.92±0.25)% and (25.03±0.18)%. The optimized technique featured by continuous varied adding rate provides a reference method for high quality production of germinated brown rice.