This research was aimed to study the student’s background in vector and the effectiveness of traditional lecture on vectors. The first year physics student were asked to do the vector evaluation test (VET) before attend the vector lesson. Vector is the first lesson of introductory physics for physics student. They had done the VET again after finishing the vector lesson. The pre-test and post-test were analyzed by using statistics and model analysis method, both individually and class model. It was found that the student had less background in many topics of vectors. The learning model also represented that many students were using their own model or common sense to solve the problem. The post-test was show little improvement on their understanding forward vectors, but they were got better in vectors production. It can be concluded that the traditional lecture had low effectiveness on vectors lesson. The other teaching method with classroom-based action research could be the key of improvement.