根据光传输理论和水体光学衰减规律，提出了水下光源主光轴上光谱辐照度随距离分布的理论模型，确定了模型结构。在此基础上，采用数值计算的方法对模型中各待定参数进行求解，根据模型结构特点提出了对不同参数进行分步拟合的思路并给出了具体的参数求解方法。为了验证建模方法的准确性和可行性，根据水下光源实测数据进行建模并对模型的精度进行了评估。结果显示：模型拟合数据与水下实测数据吻合程度较高，拟合误差的方均根值仅为实测数据方均根值的4%，说明模型拟合精度较高。该方法有望用于水下光场建模、水下图像处理等应用领域。

A model for spectrum irradiance distribution with respect to the distance in the optical axis of underwater light sources was proposed based on the theory on light propagation and the attenuation of water on light. Model structure was built from physics and unknown parameters were determined by numerical methods. By utilizing the specific structure of the model, an identification approach was proposed where independent parameters were determined in different steps. The procedures for parameter identification were given in details. To validate the accuracy of the model and the feasibility of parameter identification, the model was further tested with underwater measurement data of an artificial light source. Results show that the model estimation is quite close to the measurement data and the root-mean-square value of the modeling error is only 4% of the measurement data, thus indicating high accuracy of the model. Application of this method can be found in modeling of underwater light field and underwater image processing.