Catadioptric　imaging　systems　are　widely　used　in　many　applications　such　as　robot　navigation,　surveillance　or　3D　reconstruction　due　to　their　large　field　of　view.　However,　the　catadioptric　image　has　a　larger　deformation　than　the　perspective　image,　which　makes　catadioptric　camera　calibration　more　difficult.　Previous　approaches　using　lines　need　conic　fitting,　which　is　a　hard　work　for　catadioptric　images.　This　paper　proposes　a　nonlinear　method　based　on　the　constraint　from　the　projection　of　a　space　line.　A　simple　and　intuitive　estimate　of　the　initial　camera　parameters　is　also　presented,　which　can　be　used　in　some　applications　without　requirement　for　high　accuracy.　The　proposed　method　needs　no　conic　fitting　that　highly　affects　the　calibration　accuracy.　The　validity　of　the　proposed　approach　is　shown　by　experiments.　©2010　IEEE.