Abstract: The paper presents a method of image edge detection based on multi-structure and multi-grade weighted combination of mathematical morphology，in which the idea of morphological filter is used and on the anti-noise operators of morphological based on single-structure are improved.In this method，the fixed mean with the peak-value SNR（Signal-to-Noise） is replaced，which is tested a self-adaptive method.The experiment result compared with traditional morphological methods shows that this method remains good detected edge of image and can improve the denoising power as well.