I think for language centers, about one month salary is pretty standard bonus - but it usually comes at the end of the contract.

I worked at a university. I got regular pay for 10 months of the year. They reimbursed some of my flight (10,000 RMB) equal to 2 months of pay. Unfortunately that was just over paying back a one way flight ticket for me. I also got 1,100 RMB per semester for travel expenses. I've heard that the "flight reimbursement" is often lower, but I think mine was fair. It was like getting paid for every month of the year, even though I only worked 9 months.

There is no standard amount but I suggest it's a good idea to discuss it during the contract signing. Negotiate it.

i dont reallythink its a bons basically covers air fare 10000 rmb they calll it a bonus but it really isnt

Almost people with all jobs will get bonus before the Spring Festival.As for the amount,it depends on your performance and  position.Usually the bonus is equal to one or  two or three months' salary.