Can a subsidiary guarantee the parent company?

You can't.

In order to prevent the parent company from abusing the guarantee resources, the law stipulates strict restrictions by controlling the subsidiaries to harm the interests of other creditors. These restrictions include: the subsidiary must be approved by the resolution of the shareholders' meeting or the shareholders' meeting, and the resolution must be publicly disclosed; Subsidiaries must disclose important information such as their relationship with the parent company to creditors; Subsidiaries must fulfill the obligation of good faith disclosure to creditors.