A pre-softening dyeing process for polyacrylonitrile fibers is disclosed. The process includes five steps, namely a step of pretreatment and dyeing, a step of adding a softener into a cylinder and circulating, a step of cooling and cleaning and fixation, a step of cleaning and drying and a step of discharging and detecting. The objective of the process is to simplify and combine steps. In dyeing processes, the softener is added at a specific process point under specific process conditions to allow dyeing and softening to be completed at the same time, thus saving after-treatment time and costs of various resources on the premise of not increasing the dyeing time, and making a significant contribution to environment protection and energy conservation.