Matthew John Davey appeared in court on Wednesday where he pleaded not guilty to all charges.
Police alleged Davey doused his fiancee Nicole Louise Evans with an accelerant before setting her alight.
Evans is now in an induced coma, the court heard.
A Tasmanian woman remains in a critical condition with burns to more than half of her body after an alleged assault by her boyfriend.
Police arrived at the home on Corranga Drive in Chigwell, north of Hobart, on Monday night to find a backyard shed engulfed in flames.
The 20-year-old woman was flown to Melbourne's Alfred Hospital and her 34-year-old boyfriend was charged with causing grievous bodily harm and three counts of assault.
"The dispute is being treated as a family violence incident, although there are no current family violence orders restricting the man and woman from being together," police said.
The man also suffered burns to his body and is undergoing treatment at the Royal Hobart Hospital under police guard.
“[The woman] is in a very critical condition," Glenorchy detective inspector Craig Joel told reporters on Wednesday. "It’s very sad. I would say that her condition is grave and we are holding out the most hope for her. Our priorities are to find out what happened to this young woman."
If you or someone you know is experiencing violence and need help or support, there are national and state-based agencies that can assist you 24 hours a day, seven days a week. Call 1800 RESPECT (1800 737 732).