The hospital and patient are in the state of asymmetric information in the medical market. By developing game model, the authors analyze the game process and equilibrium between the hospital and patient under asymmetric information. The analyses demonstrate that asymmetric information can lead to low efficient equilibrium. Therefore, the hospital should set up medical information opening system and strengthen the communication between the hospital and the patient so as to relieve the situation of asymmetric information. Meanwhile, the paper puts forwad some measures about government regulation in medical marcket.