Aiming at the problem of spectral line interference caused by tungsten electrode excitation in the particle flow-spark induced breakdown spectroscopy, a spectral line interference correction method based on plasma signal detection optimization is studied. The PF-SIBS measurement experimental system was set up. The particle flow of pure chemical graphite was taken as the research object. According to the generation and extinction process of plasma between electrodes, the distribution of characteristic spectral lines in the plasma and the variation of signal intensity of characteristic spectral lines between electrodes, the evaporation, dissociation and excitation process of characteristic elements in the plasma are analyzed, and based on this, the optimal spectral detection position is optimized. The research results show that electrons are generated in the cathode spot, and electrons collide with the electrode metal, graphite particle flow and air medium between electrodes during the process of emission to the anode, resulting in more electron emission, thus forming and maintaining the discharge channel from the cathode to the anode. In the cathode region, the Joule heat generated by the high-energy electric field promotes metal evaporation and sputtering at the cathode tip, and the impact of the expansion causes particles and air to be expelled from the cathode region, and the atoms and electrons of the tungsten metal occupy the cathode area. In the middle of the discharge channel, electrons collide with the dense flow of graphite particles and ionize. In the anode region, the remaining discharge energy is difficult to evaporate the anode metal, and the electrons mainly ionize the air medium. Thus, the region from the cathode to the anode is divided into a cathode metal excitation region, a middle particle excitation region and an anode air excitation region. The ions and neutral atoms of the ionized electrodes metal, graphite particles and air medium occupy their respective excitation regions, forming plasma and radiating corresponding characteristic spectral lines. The characteristic spectral line intensity change from cathode to anode shows the same results as above, The intensity of W 247.78 nm spectral line is stronger in the cathode region and shows a decreasing trend; C 247.86 nm increased first and then decreased and reached the maximum at the center of the electrode spacing; N 744.23 nm gradually increased and reached the maximum at the tip of the anode. Using the C-W signal intensity ratio as the evaluation index of the C-W spectral line interference degree, the optimal spectral detection position was determined to be 0.5 mm away from the anode. Compared with the common spectral detection position (the center of the electrode spacing), the C-W signal intensity ratio increased from 1.200 to 1.348. The ratio of the peak fitting value of C 247.86 nm signal intensity to the observed value increased from 86.02% to 94.93%, and the C-W spectral line interference effect was significantly reduced.