A divergent intramolecular reaction of phosphine tethered alkyne in protic solvent was developed. This provided a novel and simple access to a large variety of ( Z)-alkenylphosphine oxides and phospholane oxides. Our preliminary studies suggested that these divergent reactions are closely related to the reaction condition and molecular structure. A possible mechanism of C-P bond cleavage of a pentacoordinated hydroxyphosphorane intermediate was proposed.