To be able to work legally in China, foreign workers must have: (i) a work permit linked to a specific employer, and (ii) a residence permit for work purpose. Foreign students are not eligible to obtain such permits, but enjoy some flexibility to do internships in mainland China:

• Foreign students studying in Chinese universities – and therefore already based in China – can apply for a modification of their residence permit for study purpose, after receiving written approval from the university’s overseas student office. An internship remark is added on the residence permit, only after which students can legally start off-campus internships.
• Foreigners studying in foreign universities and based abroad only have one option: being invited for internships by “renowned” enterprises or institutions based in China. In this case, foreign interns need to apply in Chinese consulates in their home countries for an S2 visa with an “internship remark”, which will have a maximum duration of 180 days.

It is strongly advised not to enter China for work with other categories of visas, such as tourism or business. Although a common practice before the COVID-19 pandemic, this is illegal and can lead to detainment and even deportation (and consequent multi-year ban from re-entering China).