Firefighters were called to extinguish the blaze near the intersection of Mauna Loa Street and 7th Street around 6:37 a.m. Once they put out the flames, they discovered the man's partially dismembered remains.
Deputies have questioned neighbors but apparently no one saw the body set ablaze or suspect.
Homicide investigators will look into whether an accelerant was used when the body was set on fire, said Cindy Bachman of the San Bernardino County Sheriff's Department.
Hesperia police have not released any information on whether the man was set on fire before or after he died. The coroner will determine the cause of death.
"The identification, the race, the age, all of that is unknown pending an autopsy," Bachman said.
Anyone with information is urged to contact Detective M. Avila at (909) 387-3589 or Sheriff's dispatch at (760) 245-4211.