Is it reasonable for security companies to work 12 hours a day and have no rest days at night according to the national labor law?

Working 12 hours a day is obviously against the labor law. You can complain and report to the local labor inspection brigade, and you will certainly safeguard your legitimate rights and interests and make compensation.

Article 36 of the Labor Law The state practices a working-hour system in which laborers work no more than eight hours a day and no more than forty-eight hours a week on average.

Article 38 The employing unit shall ensure that workers have at least one day off every week.

Article 89 If the labor rules and regulations formulated by the employing unit violate the provisions of laws and regulations, the labor administrative department shall give a warning and order it to make corrections; If it causes damage to workers, it shall be liable for compensation.