[Purpose]To analyze the incidence and mortality of thyroid cancer in Zhejiang cancer registration areas in 2021 and trends from 2000 to 2021.[Methods]Based on cancer data from 22 registries across Zhejiang Province between 2000 and 2021,the crude incidence/mortality rates,age-standardized incidence/mortality rates of thyroid cancer by Chinese and world standard population(ASIRC/ASMRC,ASIRW/ASMRW),cumulative rate(0～74 years old)and truncated rate(35～64 years old)were analyzed.Joinpoint regression model was employed to calculate the annual percentage change(APC)and average annual percentage change(AAPC)with 95％confidence in-terval(CI)for analyzing trends of thyroid cancer incidence and mortality rates from 2000 to 2021.[Results]The crude incidence rate of thyroid cancer increased from 3.62/105 in 2000 to 79.66/105 in 2021,and ASIRC rose from 3.11/105 to 69.49/105(AAPC=15.55％,95％CI:14.65％～16.61％).The AAPC for ASIRC was slightly higher in female(15.54％,95％CI:14.71％～16.49％)than that in male(15.02％,95％CI:13.53％～16.82％).The increase was significantly more pronounced in rural areas(AAPC=23.34％,95％CI:21.48％～25.33％)compared to urban areas(AAPC=14.12％,95％CI:13.15％～15.43％).Among age groups,the age group of 15～44 years old showed the fastest increase in crude incidence rate(AAPC=20.37％,95％CI:18.46％～22.31％),followed by the age group of 45～64 years old(AAPC=18.41％,95％CI:16.65％～20.19％).Between 2000 and 2021,the crude mortality rate of thyroid cancer rose from 0.34/105 to 0.56/105(AAPC=5.52％,95％CI:3.45％～7.70％),the trend of ASMRC was relatively stable.[Conclusion]From 2000 to 2021,the incidence of thyroid cancer in Zhejiang Province increased markedly,especially among females and younger to middle-aged adults,while the age-standardized mortality rate remained stable.