This paper introduces the Crofton formula of differential geometry, and clarifies the meaning of each variable. Furthermore, in order to verify the identity of the Crofton formula, the lengths of several special curves have been accurately calculated by Matlab programming, and have been compared with the actual lengths. At the same time, the Crofton formula is transformed from the calculation of the double integral to the calculation of the micro-element, so that it is easier to find the approximate solution to the general curve by Matlab programming. It is concluded that this method can be used to find an approximate solution for the length of any general curve. This template explains and demonstrates how to prepare your camera-ready manuscript for publisher. The best is to read these instructions and follow the outline of this text. Please make the page settings of your word processor to A4 format (21 x 29, 7 cm or 8 x 11 inches); with the margins: bottom 1.5 cm (0.59 in) and top 2.5 cm (0.98 in), right/left margins must be 2 cm (0.78 in). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.