Two trackers at same time?

[KFlint]

but is accepted to do this ?

why not? nothing bad doing so!

[TheFoX]

Since most trackers now modify the HASH to stop ghosting, you will find identicle torrents from different trackers use a different HASH. You may find that seeding to the public trackers work, but don't expect many private trackers to work.

[ceasar]

Just add an announce address with the passkey in properties of the torrents and you can seed same torrent on couple sites at the same time.