In solid oncology, on fluorescence microscopy images of interphase nuclei processed with fluorescence in situ hybridization (FISH) technology, DNA amplification often appears as diffraction-limited blobs. Imaging conditions limit image quality, resulting in a low image signal-to-noise ratio of the image, serious background interference, and non-blob structure interference. Designing suitable blob detection methods to provide objective and quantitative data helps doctors diagnose cancer. The algorithm first uses three-layer wavelet multiscale summation to denoise the fluorescence image, then uses the multiscale Laplacian of Gaussian operator to enhance the blob area, and finally suppresses the non-blob area through unilateral second-order Gaussian kernels in four directions to complete blob detection. Experimental results show that for 83 images in the self-built database, the average F-score reaches 0.96, and the average running time is less than 0.5 s.