The present invention provides a microstructured hollow-core optical fiber. The optical fiber comprises first type medium circular tubes, second type medium circular tubes, and a third type medium circular tube; the first type medium tubes are nested in the second type medium circular tubes and are periodically distributed along the circumference of the second type medium circular tubes; intervalsbetween the outer walls of the adjacent first type medium circular tubes are greater than 0; the second type medium circular tubes are nested in the third type medium circular tube; and the first type medium circular tubes, the second type medium circular tubes and the third type medium circular tube are connected with one another in a tangent or intersecting manner. According to the microstructured hollow-core optical fiber of the invention, confinement loss can be lowered by simply increasing the number of the second type medium circular tubes, so that a difficulty that the confinement lossof a negative-curvature anti-resonant hollow-core optical fiber cannot be reduced by simply adopting a means of increasing annular layers which assists in reducing the confinement loss of a hollow-core photonic band gap optical fiber can be eliminated. According to the optical fiber provided by the invention, too many nodes will not be introduced into the cross section of the optical fiber, and anew scheme and idea can be provided for the design and manufacture of a broadband low-loss hollow-core optical fiber.