The hospital and patient are in the state of asymmetric information in the medical market, which could lead to moral hazard, adverse selection, and low market efficiency. By the game model, we analyze the game process and equilibrium between the hospital and patient under the condition of asymmetric information. The analyzing result suggest that asymmetric information in the medical market is harmful to the patient's benefit and the development of the medical market. Therefore, it's necessary to set up medical information opening system and strengthen the communication between the hospital and the patient so as to relieve the asymmetric information between hospital and patient.