Two kinds of joule heat driven nylon coiled fiber based artificial muscles were prepared by twisting of silver- coated nylon fibers and co- twisting of silver- coated nylon fibers with conventional nylon fibers. The actuation behavior of the two coiled polymer fiber based artificial muscles was systematically studied by programming the frequency, magnitude and number of cycles of the input electric power. The results show that the electrical resistance of the coiled composite nylon fiber based artificial muscles is regulated by co-twisting. At the same input electric power, the coiled composite nylon fiber based artificial muscles generate a higher temperature and exhibit better actuation performance. The results show that coiled silver-coated nylon fiber based artificial muscles exhibit a maximum actuation stroke of 6.34%, a maximum work density of 382 J/kg, and a maximum power density of 468 W/kg. The coiled composite nylon fiber based artificial muscles exhibit a maximum actuation stroke of 7.42%, a maximum work density of 428 J/kg, and a maximum power density of 531 W/kg. The actuation of the two coiled polymer fiber based artificial muscles can exceed 1×10⁴ cycles, and its actuation strokes have no obvious decrease.