We don't know. Judging by Paul's writings, it seems unlikely that Jesus had long hair because Paul orders in Scripture for men to keep their hairstyles short so as not to boast about their appearance.
We know that the Jewish priest wore his hair as long as possible on the side of his head, but cut it at ear level on top to show that he was required to avoid all other forms of adornment except that prescribed by the law. There is no evidence that Jesus followed these guidelines during his lifetime, and it is quite likely that he did not follow them after he rose from the dead either.
The Jewish culture of the time was a strict monotheistic society, and many of its laws were adopted by Judaism. One such law states that Jews keep their hair at least one inch from the scalp - long enough to be gathered, but not as long as typical women's hair when uncut.