The invention provides a measurement and transmission apparatus for marine riser fatigue parameters and a calculation method of optimal repeater spacing. The apparatus comprises an underwater sound signal receiving device, a plurality of repeaters and a marine riser fatigue monitoring device. The marine riser fatigue monitoring device detects a fatigue signal and transmits the fatigue signal to the repeaters; and after multiple transmissions by the repeaters, the fatigue signal is transmitted to the underwater sound signal receiving device. According to calculation of energy consumption of different repeater spacing single hop links, total transmission energy consumption of employing different repeater spacings is figured out, thereby figuring out the optimal repeater spacing corresponding to a lowest total transmission energy consumption by comparison. The invention employs repeaters to shorten a signal transmission distance, reduce transmission power consumption of a single hop distance; besides, an optimal distance scope exists, so as to realize a lowest total transmission energy consumption.