Event Data Recorder (EDR) is a device to record vehicle and occupant information for a brief period of time before, during and after a crash event. EDR is one of the promising devices for accident reconstruction by recording important information e.g. vehicle speed, engine speed, brake switch, throttle and delta-V. However, in order to use EDR for an accident investigation, reliability and accuracy of those EDR data must be examined firstly. The aim of this study is to evaluate the characteristics of EDR and to understand the performance of EDR for the improvement of accident reconstruction with more reliable and accurate information on an accident in Japan. The analysis is based on J-NCAP crash tests from 2006 to 2009 with corresponding EDR datasets. Full-overlap frontal collision test and offset frontal collision test of fourteen car models were analyzed. The pre-crash velocity and the maximum delta-V data recorded in the EDRs are compared with the results from accelerometers and from high speed video cameras. In all cases, the pre-crash velocity recorded by the EDRs showed good reliability and accuracy. Moreover, thirteen crash tests were conducted to understand the performance of EDR under the situation of real world traffic accidents. The crash test types were frontal crash tests (collide to offset rigid barrier and concrete block), pole crash tests (front-center with iron pole, front-right with iron pole, right side with iron pole and front-center with concrete pole), car-to-car collision tests and multiple rear-end collision tests. The pre-crash velocities of EDRs showed good reliability excluding cases with full braking condition. Braking condition may influence the recording data as over estimating. On the other hand, the EDR longitudinal delta-V from pole crash may indicate less reliability. Principle direction of force (PDOF) is estimated and evaluated using EDR recording data.