Is it reasonable for the company to say that it will only buy social security after working in the company for one year? Is there a solution?

Unreasonable. However, from your point of view, if you still want to work here, you should bear it first and keep your employment certificate with your employment date on it. When you plan to leave your job, ask the company to make up the social security owed to you from the date you joined the company, otherwise you can report it to the labor bureau or take the evidence to the arbitration department. Both methods can get the most satisfactory results.

My previous company gave me two years less insurance, and I didn't look for it, because I was still young and didn't care. Now this company has given insurance and provident fund since I joined the company, and I have been on probation. It is better to enter a regular company. Many procedures are reasonable and legal.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.