A comparison was made between the effects of the ginger and alum processing method (referred to as the pharmacopoeia method) recorded in the 2020 edition of the Pharmacopoeia of the People's Republic of China and the expansion method on Arisaematis Rhizoma, aiming to explore a new efficient processing method for reducing toxicity while preserving efficacy. The raw Arisaematis Rhizoma was processed using both the pharmacopoeia method and the expansion method. The contents of trigonelline, schaftoside, and isoschaftoside were determined by HPLC. The total flavonoids and total saponins were measured by ultraviolet-visible spectroscopy. The quality evaluation and toxicity-reducing effects of the samples processed by the two methods were compared based on structural changes of calcium oxalate needle crystals and lectin activity. The expectorant effects of the processed Arisaematis Rhizoma were pharmacodynamically studied using the tracheal phenol red method in mice. The results showed that the expansion-processed products had significantly higher contents of total flavonoids (0.830 mg/g), total saponins (3.333 mg/g), trigonelline (559.473 μg/g), schaftoside (45.759 μg/g), and isoschaftoside (26.687 μg/g) compared to the pharmacopoeia-processed products. Additionally, the expansion-processed products contained no alum, the calcium oxalate needle crystals were completely destroyed, the agglutination activity of Arisaematis Rhizoma lectin disappeared, and the expectorant effect was 1.3 times that of the pharmacopoeia group. Based on the results of various indicators and pharmacodynamic studies, the expansion processing method is significantly superior to the pharmacopoeia method and can be used as a new method for large-scale processing of Arisaematis Rhizoma.