If your study visa will expire in 4 weeks, you are required to apply for 'Extension of Stay' at the Immigration Department.  For details, please visit the website of the Immigration Department at:

www.immd.gov.hk/eng/services/visas/study.html#extension_of_stay&firstTab

If you need to re-apply for your study visa (i.e. your current limit of stay has expired), please prepare the Application form ID 995A and the required documents, which can be downloaded at

www.cuhk.edu.hk/osa/iss/usefulinformation.html, and send them to the Incoming Students Section, Office of Student Affairs for further processing.

For both applications, you are required to submit a certifying letter issued by the Registration and Examinations Section.  You may apply online at

https://rgsntl.rgs.cuhk.edu.hk/rws_prd_life/rws_appl/appf_crtltr_ug.asp