The optical detection of the crosslinking degree is very important to the forming quality’s on-line control of the hydrogel fibers and tissue engineering scaffolds in 3D printing process at room temperature. For the feature of small scale object, low contrast ratio and unclear outline of the crosslinked area, we processed the crosslinking image with the dual-threshold enhancement method. Firstly, the color image is decomposed into three two–dimensional RGB signals. Secondly, the RGB signals are processed through wavelet transform respectively, and those wavelet coefficients are amplified or reduced with dual-threshold method for the purpose of enhancement and denoising. Then, the new RGB signals are reconstructed by those wavelet coefficients. At last, the new RGB signals are regrouped to get enhanced crosslinking image. Experimental results show that, after processed with this method, the image has a strong sense of color gradation, the details of image are outstanding, and the distinction of the crosslinked zone of the hydrogel fiber is obvious. Moreover, measurement precision of crosslinking degree is improved by 4.58%. This is helpful to improve the performance of the real-time control of crosslinking process.