His mother, who tried to save her, was critically injured.
The incident happened at Surahibag village in Itkhori police station area on Thursday night, they said.
The accused, Kuldeep Kumar Dangi, is on the run since the incident, police said.
“Raids are on to nab him,” Itkhori police station in-charge Vinod Kumar Yadav said.
Dangi used to beat his wife regularly after getting drunk, he said.
“On Thursday night, he assaulted his wife under the influence of alcohol. He then set her on fire after pouring kerosene. His mother came to her rescue, and she received 80 per cent burn injuries,” Yadav said.
The body of his wife was sent for postmortem, while his mother was admitted to RIMS in Ranchi.
With PTI inputs