The invention discloses a preparation method of bamboo fiber threads for desert greening water conveying. The method comprises the following steps that bamboo tubes with the bamboo joint length of 500mm or above are selected, bamboos are cut off at bamboo joints, bamboo joints at the two ends of each bamboo tube are removed, and remaining parts are cut into bamboo sheets with the width smaller than or equal to 30 mm, boiled at high temperature for 12 h and taken out; the two ends of each bamboo sheet are fixed to torsion pulling devices which can rotate relative to each other and repeatedly rotate until the bamboo sheet is loose bamboo fiber strands; the obtained bamboo fiber strands are combed into bamboo fiber strands with the diameter smaller than 5 mm and the length larger than 300 mm, and the bamboo fiber strands are parallelly arrayed, vertically immersed into a water-absorbent resin solution at 45 DEG C for 20 min, shaped, dried and cut. According to bamboo fiber yarn which isused for greening cultivation water conveying and manufactured by using the bamboo fibers, the application of the fiber yarn in the desert cultivation process can be effectively achieved, the water absorption performance of the bamboo fiber threads is stable, a water source can be stably conveyed to plants for a long time, and the survival rate of the plants is increased.