A growing number of traffic accidents have occurred in recent years. The determination of the main liability in traffic accident will cause controversy. Crime scene investigators need to fix the scene of the accident by photography and field survey measurement. However, some inaccuracies and omissions may occur when taking a photograph due to many reasons and thus cause some problems in determination of traffic accident liabilities. By applying imaging perspective measurement method and image superposition method with Photoshop CS4 (Referred to as PS) software, it can solve part of these problems. We take a traffic accident occurred in Shaanxi province for example to illustrate. When the crime scene investigators took a photograph at the scene of the accident, they missed some details, which made it difficult to determine the liabilities. Then the methods mentioned above was used and the results indicated that the car parking between the slow lane and the emergency lane should be mainly responsible for the accident. The experimental results demonstrate that imaging perspective measurement method can be accurate and the image superposition method can provide a reference. The actual application should also depend on the specific situation.