The laser detection technology based on orbital angular momentum (OAM) beam has been rapidly developed, but it is restricted by many factors from being applied in practice. One of the most significant issues is that it is greatly affected by environmental conditions. When it is applied in the fog environment, the signal-to-noise ratio (SNR) of the echo signal will be seriously reduced due to the interference of environmental noise. A comprehensive study on the forward propagation and backscattering characteristic evolution theory of OAM transmission through the atmospheric fog environment is essential to formulate corresponding strategies to improve its environmental adaptability. In this work, we proposed a light field initialization method based on the Acceptance-Rejection Method (ARM) which can convert the light field to photon flow. By combining this method with the Electric Monte-Carlo (EMC), we established a propagation dynamics analysis model of OAM beam in a fog environment to reveal the propagation and evolution process of OAM beam in a complex environment. This work provides the theoretical and technical support for improving the applicability and detection accuracy of OAM laser detection technology in a complex environment. Furthermore, by combining with other models, this model can be updated for analysis of the transmission dynamics of multidimensional modulated light field under more complex environment conditions, such as foggy, smoky, and rainy environments, which can help to improve the performance of free space optical communication, Lidar, and laser energy delivery systems.