The invention relates to a highway tunnel natural ventilation method and system based on the chimney effect and belongs to the technical field of highway tunnel operation ventilation. According to the method, a solar chimney is arranged in a highway tunnel, the solar radiation is used for heating the air in a chimney channel, buoyancy lift is provided for air movement in the tunnel, the temperature difference is increased, and natural ventilation is intensified. The ventilation system is integrally in a chimney shape, and the whole system is installed in a longitudinal ventilation shaft of the tunnel in a wall-adhesion mode. The lower end of the ventilation system is communicated with the air in the tunnel, and the upper end of the ventilation system is communicated with the atmosphere outside the tunnel. The installation inclination angle of the ventilation system is alpha so that the solar radiation can be absorbed better. The part, facing the sun, of the upper part of the ventilation system is made of light absorption materials, the lower part of the ventilation system is an absorber plate, and the middle of the ventilation system is an air flow channel. During working, the air in the ventilation shaft can receive the solar heat absorbed by the absorber plate, the increasing of the air heat can accelerate upward removing of the air from the tunnel, and then the air removing effect is enhanced.