Abstract: An efficient algorithm for calculating the fiber-placement paths over the pipy-shape parts based on generatrices is proposed. Firstly, we construct a few key control generatrices according to the shape of the pipy parts, then produce all generatrices by interpolating these key control generatrices; paths are finally determined by putting together all the generatrices following the constraint of constant angle placement. Technical issues regarding path's intersection and clearance are discussed, and a strategy of precision control over the tow-placed part is promoted. We implemented our algorithm under the environment of CATIA V5R14 and its 3rd party development platform, and verified its validity through an application on aircraft S-inlet.