I pay social security in Zhoushan and Shanghai. Can two accounts be merged?

A person cannot have two social security accounts at the same time. You can have social security accounts in two places, but after you retire, the two accounts will be merged into one, because you can only receive your pension in one place, so it will not be cheap for you to receive your pension in two places at the same time. You can choose where to receive your pension. If both of your accounts are paying social security at the same time, you will only suffer in the end. Take your situation as an example. Suppose both of your accounts are paying social security, and you choose a Shanghai account when you retire. The personal account in Zhoushan account will be transferred to your Shanghai account, but the transferred money is estimated to be less than a quarter of your accumulated Zhoushan account. In other words, most of the money you pay to Zhoushan account will not be yours in the end, and it has been attributed to Zhoushan's social co-ordination part. I don't know if I made it clear, hehe.

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