To address the problems of low detection accuracy and small detection area of the traditional Ring Oscillator (RO), a structure-optimized RO is proposed by improving the structure of the traditional RO, which improves the Trojan detection rate and detection area by increasing the contact area with the Trojan circuit. The experimental results on FPGA show that, compared with the traditional RO detection method, the structure-optimized RO has the following advantages The experimental results on FPGA show that the structure-optimized RO has the following advantages over the traditional RO detection method: 1) it can accurately detect a hardware Trojan with only 20 logic cells; 2) it expands the detection area of RO by about one time.