Raman spectroscopy plays an improtant role in analytical science because of its unique characteristics, such as non-contact and non-destructive detecting, fewer sample consumption, high sensitivity and other characteristics, and it provides a powerful analytical tool for the modern basic research fields. Because of the combination of confocal microscopy technology and Raman spectroscopy technology, confocal Raman microscopy has the advantage of both high resolution spectroscopy and chromatography detection, which inherits from confocal microscopy and raman spectroscopy. As a result, it is widely used in many fields, such as physical chemistry, materials science, biomedical, archaeological, cultural identification, and forensic science. But with the environmental changing, the system drifting or other issues, during the long detection process, the system turns to defocusing. As a result, during the hole scanning process, the system can not be focused on every detection point, and then it would lead to a mistake. Eventurally, conventional confocal Raman system could obtain the presence of measurement error even erroneous results in the long process. In this paper, on the basis of conventional confocal Raman system, a confocal Raman spectroscopy method based on quadratic curve fitting is proposed to solve this problem. Based on the principle that the maxium of the concal curve corresponding the system foucs, the steps to find system foucus as follows: fist, usesing quadratic curve to fit confocal curve; second, finding the maxium of the confocal curve; and last obtaining the system foucs. With this method, during the scanning process, every point should be focused, therefore, the effect of defocusing is eliminated efficiently, and accurate measurements of confocal Raman spectroscopy system is achieved.Through simulation and experimental results show that: the proposed method that confocal Raman spectroscopy method based on quadratic curve fitting can effectively eliminate the influence of system defocus on experimental result, and effectively improve the axial system of fixed focus accuracy, which could provide a guarantee for further application of confocal Raman spectroscopy. This anti-drift method is effective and accurate in focusing with great potential to be applied in broader areas.