The board of supervisors consists of more than three people, among whom there must be employee supervisors, and the proportion shall not be less than one third, and it shall be stipulated in the articles of association.
Then the non-employee supervisors are elected/appointed by the shareholders' meeting or the founding meeting, that is, the non-employee supervisors can hire non-shareholders or be elected by the shareholders' meeting or the founding meeting.
Employee supervisors are elected by the employee congress.
To sum up, supervisors of joint-stock companies do not necessarily have shares, and shareholders do not necessarily have shares.
Legal basis: Article 147 of the Company Law of People's Republic of China (PRC), directors, supervisors and senior managers shall abide by laws, administrative regulations and the articles of association of the company, and have the duty of loyalty and diligence to the company. Directors, supervisors and senior management personnel shall not take advantage of their powers to accept bribes or other illegal income, and shall not encroach on the company's property.