An understanding of the antityrosinase capacity and polyphenols changes during hydrothermal treatments was crucial for application of asparagus. Therefore, asparagus extract was treated at a range of 80-160 °C for 30-150 min in a high temperature reactor. The results suggested that tyrosinase inhibition rate of untreated asparagus extract was recorded as 3.26% but significantly increased to 51.22% and 50.80% after heating for 90 min at 140 °C (lnR0 of 7.21) and 160 °C (lnR0 of 8.57), respectively. The generation and degradation of polyphenols followed the pseudo-first-order kinetic model. The coumaric acid content was increased from 35.03 μg/mL to 307.66 μg/mL at lnR0 of 8.16. The degradation of rutin in asparagus extract was far less compared to that of coumaric acid. Compounds formed were determined by UPLC-Q-TOF-MS yielding main fragments at m/z 451 and 601. In conclusion, hydrothermal treatment was a feasible method for increasing the antityrosinase capacity of asparagus.