How to pay social security for two companies?

Article 57 of the Social Insurance Law of People's Republic of China (PRC), the employing unit shall, within 30 days from the date of its establishment, apply to the local social insurance agency for social insurance registration with its business license, registration certificate or unit seal. The social insurance agency shall, within fifteen days from the date of receiving the application, examine and issue the social insurance registration certificate. Where the social insurance registration items of the employing unit are changed or the employing unit is terminated according to law, it shall, within 30 days from the date of change or termination, go to the social insurance agency to handle the change or cancellation of social insurance registration. Article 58 of the Social Insurance Law of People's Republic of China (PRC), the employing unit shall, within 30 days from the date of employment, apply to the social insurance agency for social insurance registration for employees. If the social insurance has not been registered, the social insurance agency shall verify the social insurance premium it should pay.