AbstractTo realize low‐loss low‐crosstalk long‐length polarization‐maintaining fibers, this paper examines the “PANDA fibers” having a circular stress‐applying part which has a high design accuracy and ease of fabrication. Stress‐applied type polarization‐maintaining optical fibers generally have two orthogonal polarized modes, and their coupling causes crosstalk which makes the transmission of polarized mode through a long‐length of fibers difficult. To suppress this mode‐coupling, it is important (a) to make the modal birefringence larger, and (b) to reduce the deterioration of the symmetry of the stress applied. This paper examines the circular stress‐applying type PANDA fiber and compares it with two other types of PANDA fiber having the typical shapes of the stress‐applying part. As a result, (1) the structure parameters of the stress‐applying part which gives the maximum modal birefringence and a low loss, and (2) the mode‐coupling parameter, with the stress‐applying part deviated, which can evaluate the crosstalk characteristics, have been obtained. Based on the results of these theoretical analyses, the symmetry in the stress‐applying part is improved by using a large preform, and the increase of the modal birefringence by increasing the outer diameter of the fiber is carried out. The circular stress‐applying type PANDA fiber having a crosstalk as low as ‐42 dB in 1 km has been realized.