Laser welding has been widely employed for aluminum alloy body-in-white. However, owing to the low utilisation efficiency of energy and material, the carbon emission of laser welding is serious. In this paper, the mathematical modelling of carbon emissions and process parameters optimisation for laser welding cells are studied. The carbon emission characteristics of the laser welding system are analysed, and the carbon emission model of the laser welding cell considering both welding features and welding transfers is established. Besides, the process parameters optimisation model of laser welding cell is developed. To obtain optimal welding sequence, a combinatorial algorithm based on Culture Algorithm and Ant Colony Algorithm is proposed. Based on the optimal welding sequence, the optimal transfer speed is obtained through mathematical theory. Furthermore, a case study is performed to verify the feasibility and reliability of the process parameters optimisation model. Additionally, compared with the Ant Colony Algorithm, the proposed solution algorithm has better comprehensive performance in terms of convergence speed and optimisation accuracy. This study lays a theoretical foundation for carbon emission modelling of the laser welding cell, and can support the automobile enterprise to make processing parameters selection of the laser welding line in the design stage.