The invention relates to a body fitness machine, which includes a flat belt, a transmission belt, two sets of connecting rod booms and pedal sets, two sets of mutually symmetrical belt length adjustment cams, a transmission resistance system, a movement arm resistance system, and a belt loosening prevention system. device. It is characterized in that: the transmission resistance system includes two cranks (21), the central shaft (16), the belt pulley (6), the dead center assist system (9), the tension pulley (7), the belt (18), the belt ( 19), ECB magnetically controlled resistance wheel (12), two hoisting bearing housings (17) and two belt fixing clips (20); the dead center power assist system (9) includes 3 cylindrical strong magnets with a magnetic force of 7000 Gauss (92), adjustable magnet sleeve (93), magnet sleeve (91), fixed frame (94), hexagonal thin nut (95); boom resistance system: including boom connecting rod (13), synchronous pulley (10 ), magnetic control wheel (14), timing belt (26), belt fixing U-shaped (22) and belt tensioning U-shaped (21); the present invention has low noise, little power consumption, and fits different exercise habits of users.