The invention discloses a water sample collection point positioning device, and relates to the technical field of water sampling. The water sample collection point positioning device comprises a frame, a main rod and at least one positioning rod perpendicular to the main rod, wherein the frame comprises a first rod, a second rod, a third rod and a fourth rod connected end to end sequentially; the first rod, the second rod, the third rod and the fourth rod are connected by pin shafts in a rotating manner; the pin shaft for connecting the second rod with the third rod is fixed on the main rod; the pin shaft for connecting the first rod with the fourth rod can slide along the main rod; the positioning rod is connected with the frame in a sliding manner; the positioning rod equally divides a distance between the pin shaft for connecting the first rod with the third rod and the pin shaft for connecting the second rod with the fourth rod. The water sample collection point positioning device realizes the technical effect of dividing water layers with different water depths at precise intervals by the positioning rod, ensures representativeness of collected water samples, and further provides effective detection data for objectively reflecting actual distribution conditions of fertilizer at different water depths.