Parkinson's disease (PD) is a severe neurodegenerative disease and there is great need for developing a biochemical detection method to precisely diagnose it. Alpha-synuclein (α-syn) participates in the main pathology of PD and serves as an important biomarker of PD. Here, we identified peptoid ASBP-7 that had high affinity and specificity to α-syn by screening a peptoid library using the high-throughput surface plasmon resonance imaging method. We confirmed that ASBP-7 could significantly distinguish PD sera from the normal ones through identifying α-syn in the serum. We also demonstrated the high sensitivity of this system in detecting PD serum. This work provides a method for the blood-based, label-free, high-throughput analysis of PD serum, and holds great potential for the early diagnosis and dynamic monitoring of PD.