The invention belongs to the technical field of traffic safety, and discloses a method for quantifying a behavior risk of a driver in a highway tunnel environment. The method comprises the steps: collecting the real-time speeds of corresponding speed sampling points when each driver passes through a tunnel entrance segment, a tunnel travelling segment, a tunnel exit segment and a common highway segment, and enabling the real-time speeds to serve as the subjective expected vehicle speeds of the drivers; obtaining the vehicle speed of each driver at a 50 position of each segment; calculating the highest and lowest safety vehicle speeds of each segment; obtaining an objective safety vehicle speed according to the highest and lowest safety vehicle speeds of each segment; obtaining the safety vehicle speed difference of each driver at the corresponding speed sampling points of each segment according to the subjective expected vehicle speed and objective safety vehicle speed of each driver at the corresponding speed sampling point of each segment, and enabling the safety vehicle speed difference to serve as a behavior risk quantification index of the corresponding driver, wherein the larger safety vehicle speed difference at the corresponding speed sampling point indicates the higher behavior risk of the driver at the speed sampling point of the corresponding segment.