The invention provides a method for solving the problem of adjacent channel interference through additional antenna positioning. The method comprises the following steps of: 1, arranging an additional antenna; 2, dividing a scaling point; 3, calculating the distance between the original antenna and the scaling point, and the distance between the additional antenna and the scaling point; 4, determining the basic link transmission loss of the original antenna and the additional antenna relative to the scaling point; 5, theoretically calculating the uplink signal strength value of each scaling point, which is received by an original antenna receiver; 6, theoretically calculating the uplink signal strength value of each scaling point, which is received by an additional antenna receiver; 7, adjusting the uplink signal strength value of each scaling point, which is received by the original antenna receiver through actual measurement to obtain a reference value; 8, adjusting the uplink signal strength value of each scaling point, which is received by the additional antenna receiver through actual measurement to obtain a reference value; and 9, matching the reference values with the stored reference value to determine the position of a vehicle. The method can solve the problem of adjacent channel interference and improve the reliability of an electronic toll system.