Software　Effort　Estimation　is　the　process　of　predicting　the　effort　required　to　develop　a　software　system.　Many　estimation　models　have　been　proposed　over　the　last　decades.　With　the　development　of　Component-Based　Software　development,　some　new　issues　raised　up　because　that　it　is　difficult　to　estimate　cost　during　software　development　by　using　traditional　methods　or　models.　In　this　paper,　are　investigated.　Some　factors　will　effect　the　effort　estimation　in　component-based　software　development.　And　an　effort　estimation　model　for　component-based　model　is　proposed　in　this　paper.　In　this　model,　component　testability　is　considered　as　a　estimation　factor.