In 1982, Professor Fang Guoliang found the “Non full resonance” phenomenon in a tool system while he use the thin-long tool ultrasonically machining deep-small hole. He called it as “local resonance”. Also this “Non full resonance” phenomenon was discovered in the ultrasonic drilling and the ultrasonic honing system later. To its mechanism, professor Fang thought that the coupling of long-thin tool bar and driving system is weak, so the tool bar can vibrate independently, but the quantitative relation between the coupling factor and diameter ratio is not made certain. Then several theories come forth to interpret it but still haven’t a common conclusion. Through the systematic experimental and theoretical research, this paper reveals that the “local resonance” phenomenon of ultrasonic honing system has the same essence with the “local resonance” phenomenon in deep hole machining system: when the section area ratio of tool bar and driving system is small enough, some resonance frequencies of combined system are close to the resonance frequencies of “fixed-free” state tool bar, the combined system is still resonant. According to the given depth of hole and structure size, we can use the transfer matrix deduced in this paper to design flexible bar and oilstone seat not only satisfying mechanical structure size but also achieving enough magnitude. It greatly simplified the design. This new method can be named as “local resonance” design method for ultrasonic honing system. The experiment, deduction and design method have a certain common meaning to the study and design of other ultrasonic system. In 1982, Professor Fang Guoliang found the “Non full resonance ” phenomenon in a tool system while he use the thin-long tool ultrasonically machining deep-small hole. He called it as “local resonance Non-full resonance ”phenomenon was discovered in the ultrasonic drilling and the ultrasonic honing system later. the quantitative relation between the coupling factor and diameter ratio is not made certain. Then several studies come forth to interpret it but still have not a common conclusion. Through the systematic experimental and theoretical research, this paper reveals that the “local resonance ”phenomenon of ultrasonic honing system has the same essence with the “ local resonance ”phenomenon in deep hole machining system: when the section area ratio of tool bar and driving system is small enough, some resonance frequencies of combined system are close to the resonance frequencies of “fixed-free ” state tool bar, the combined system is still resonant. According to the given depth of hole and structure size, we can use the transfer matrix deduced in this paper to design flexible bar and oilstone seat not only satisfying mechanical structure size but also able enough magnitude.. The simplified method of be named as “local resonance ” design method for ultrasonic honing system. The experiment, deduction and design method have a certain common meaning to the study and design of other ultrasonic system.