The new deal also incudes the option of another year.
Speaking to the official website Ainsworth said
"This deal will take me to the age of 35, which means that of all the clubs I've played for, this is where I've been the longest.
"Gianni and Gary both said that I'd be rewarded at the end of last season and I'm glad to see they are both true to their word.
"I'd like to think I've still got a job to do here, especially when it comes to influencing the youngsters. If I can be a role model to just one of them, I'd be happy - but if I could help ten of them, I'd be over the moon.''