Legal analysis: It is illegal for the company to require employees to provide a letter of guarantee when they join the company, and the employees have the right not to provide it. General companies do not need to sign a letter of guarantee when they join the company. If it conflicts with the mandatory laws of the country, it is of course invalid, but there is no conflict. If I am willing to sign, the contract is binding on both parties. Even if it has legal effect, there are great risks.
Legal basis: Article 9 of the Labor Contract Law of People's Republic of China (PRC), the employing unit shall not detain the employee's resident identity card and other documents, and shall not require the employee to provide guarantee or collect property from the employee in other names.