The invention discloses a curve envelope fitting method based on a VGG16 network, and the method comprises the following steps: training a neural network by using a data set sample which is provided with a label and is acquired and established by a CCD, and applying the neural network algorithm to an acquired data set to verify the accuracy and calculate the microscopic morphological characteristics of the surface of an optical fiber; creating a read data set through a tenserflow framework, recording a gray value change sequence of the group of images at a certain pixel point (a, b) as X(a, b)(t), supplementing the sequence X(a, b)(t) into a one-dimensional sequence X2(a, b)(t) with the size of 224 * 224 by adopting a cubic Hermite interpolation method, and then converting the sequence X2(a, b)(t) into a two-dimensional image matrix X2(a, b)(m, n); processing and outputting the predicted actual height of the pixel point through a specially designed convolutional neural network, and comparing the actual height of the pixel point with a sample label to enable an error to be within a set threshold range. The application of the neural network enables the algorithm to have better self-learning, self-organizing and fault-tolerant capabilities and excellent nonlinear approximation capability, can improve the accuracy and fault-tolerant capability of the envelope algorithm, and has certain reference significance.