To characterize Subjective Cognitive Decline (SCD) in Parkinson's disease (PD) and its progression, as well as to assess the impact of rehabilitation training programs on cognitive function in PD patients. The study involved 42 patients diagnosed with PD. Participants underwent evaluation using a neuropsychological protocol and were subsequently classified into two groups: those with SCD (PD-SCD+, n= 22) or those without (PD-SCD-, n= 20). After an average follow-up period of 3.0 years (2.7-4.6 years), cognitive assessments were reiterated with the same group of subjects. Following the re-assessment, all 42 patients participated in a six-month rehabilitation training program, concluding with the reevaluation of cognitive performance. In the follow-up assessment, it was observed that PD-SCD+ experienced a more pronounced annual decline in cognitive function, as measured by the Chinese-Beijing version of Montreal Cognitive Assessment (BJ-MoCA) test and semantic fluency, compared to PD-SCD-. A stepwise logistic regression analysis identified low MMSE scores (P< 0.001), elevated HAMD scores (P= 0.008), male gender (P= 0.026), and the presence of SCD (P= 0.022) associated with diminished language skills in PD patients. Both groups of PD patients exhibited improvements in BJ-MoCA scores after participating a six-month rehabilitation training program. Particularly notable is the statistically significant improvement in language skills observed in patients with PD-SCD+ compared to PD-SCD- patients following rehabilitation training. As PD progresses, individuals with PD-SCD+ tend to experience more pronounced cognitive decline compared to those with PD-SCD-. Semantic fluency emerges as a crucial component for assessing the cognitive subset of PD, potentially serving as an indicator of cognitive decline in individuals with PD. Evidence suggests that rehabilitation training is a viable intervention for individuals diagnosed with PD. This intervention not only improves various cognitive domains but also leads to more substantial enhancements in language skills.