The China Communist Party (CCP) has quietly passed its Reserve Military Service Law, which will take effect on 3/1/2023. Anyone who is 18 years or older is obliged to enlist after a national defense mobilization is announced.
The notice, shown above, instructs China citizens "After receiving the call-up notice, reservists must report to the designated place at the specified time in accordance with the requirements. After the state issued the mobilization order, the reserve personnel who have not received the call-up notice shall not leave the reserve registration place without the approval of the troops and the military service organs of the reserve registration place; if they have left, they shall return immediately or standby in the same place."
Full text: http://www.npc.gov.cn/npc/c30834/202212/675bfdf572d1440d89e29080e7310b6f.shtml
Females need to serve too, except during pregnancy, maternity leave, and breastfeeding. The shortest serving time is 4 years.
Ordinary reservists can apply for discharge after reaching the age of 30. Officers need to serve until 45-60, depending on their ranks.