In　order　to　estimate　the　collision　risk　in　the　process　of　airspace　planning,　a　collision　risk　model　based　on　distribution　of　initial　time　interval　is　proposed.　In　the　collision　risk　model　given　some　airspace　planning　parameters　comprised　of　separation　minimums,　flight　segment　length,　speeds　of　aircraft,　the　proportion　of　the　aircraft　type,　flow　rate,　required　navigation　performance　value,　climb　gradient　or　descend　gradient　are　included.　The　influences　of　airspace　planning　parameters　on　collision　risk　can　be　characterized.　The　results　show　that　vertical　separation　minimum　have　greater　influences　on　the　collision　risk.　A　method　to　calculate　the　collision　risk　between　intersecting　flight　tracks　with　planning　parameters　is　developed.　These　would　provide　the　method　and　theory　to　research　the　collision　risk　in　the　field　of　terminal　airspace　planning.