A real-time image acquisition system for the morphology of deposits was established using a dimming lens, a filter lens and a charge coupled device (CCD) industrial camera. The feature sizes of deposits, i.e. deposition height and width were extracted from the recorded images based on Halcon platform. The purpose is to investigate the mapping relation and dynamic response characteristics between the process parameters and the surface morphology of deposited layers in tungsten inert gas (TIG) welding based additive manufacturing of aluminum (Al) components. Three process parameters, forming speed, arc current and wire feeding speed, were taken as the system input to investigate the step response identification and dynamic characteristics analysis of feature sizes of deposited layers. Results show that the feature size of deposited layer is the fastest in response to the arc current, the forming speed is the second, and the wire feeding speed is the slowest. The response factor of feature sizes of deposited layer is the largest in the forming speed step, the wire feeding speed is the second, and the arc current is the smallest. Time lag exists in the change of feature size of deposited layers when process parameters are adjusted. The forming speed should be selected as the primary process variable to adjust and control the feature sizes of deposited layers in dynamic control by the comprehensive consideration of the response rate and gain coefficient of feature sizes of deposited layers.