A message transmission method for a roadside equipment, wherein the message transmission method comprises: receiving information from a plurality of external sensors; receiving a road intersection sign phase information and a road map information; performing an object position analysis, a speed analysis, and a sign analysis in object moving direction based on the external sensor information, the road intersection sign phase information, and the road map information; outputting a classification of dangerous objects in different groups according to the object position analysis, the speed analysis, and the sign analysis in object moving direction; and according to a current transmission bandwidth limitation and the classification of the dangerous objects, a dangerous object message with a higher classification of the dangerous objects is preferentially selected and transmitted by a vehicle-to-road communication device within an available transmission bandwidth; wherein the classification of dangerous objects in different groups comprises determining following steps: i) when the object is on a road (L1 to L4) and the object is far away from the intersection, the object is classified into a dangerous object of group D; ii) when a sign in the object moving direction is not a green light and a speed of the object is less than a threshold, the object is classified into a dangerous object of group C; iii) when a time from the object to a stop line is less than a threshold and the object does not exceed the stop line, the object is classified into a dangerous object of group B; iv) when the time from the object to the stop line is less than the threshold and the object exceeds the stop line, the object is classified into a dangerous object of group A; wherein the danger degree of the dangerous object of group A is higher than that of the dangerous object of group B, the danger degree of the dangerous object of group B is higher than that of the dangerous object of group C and the danger degree of the dangerous object of group C is higher than that of the dangerous object of group D. receiving information from a plurality of external sensors; receiving a road intersection sign phase information and a road map information; performing an object position analysis, a speed analysis, and a sign analysis in object moving direction based on the external sensor information, the road intersection sign phase information, and the road map information; outputting a classification of dangerous objects in different groups according to the object position analysis, the speed analysis, and the sign analysis in object moving direction; and according to a current transmission bandwidth limitation and the classification of the dangerous objects, a dangerous object message with a higher classification of the dangerous objects is preferentially selected and transmitted by a vehicle-to-road communication device within an available transmission bandwidth; wherein the classification of dangerous objects in different groups comprises determining following steps: i) when the object is on a road (L1 to L4) and the object is far away from the intersection, the object is classified into a dangerous object of group D; ii) when a sign in the object moving direction is not a green light and a speed of the object is less than a threshold, the object is classified into a dangerous object of group C; iii) when a time from the object to a stop line is less than a threshold and the object does not exceed the stop line, the object is classified into a dangerous object of group B; iv) when the time from the object to the stop line is less than the threshold and the object exceeds the stop line, the object is classified into a dangerous object of group A; i) when the object is on a road (L1 to L4) and the object is far away from the intersection, the object is classified into a dangerous object of group D; ii) when a sign in the object moving direction is not a green light and a speed of the object is less than a threshold, the object is classified into a dangerous object of group C; iii) when a time from the object to a stop line is less than a threshold and the object does not exceed the stop line, the object is classified into a dangerous object of group B; iv) when the time from the object to the stop line is less than the threshold and the object exceeds the stop line, the object is classified into a dangerous object of group A; wherein the danger degree of the dangerous object of group A is higher than that of the dangerous object of group B, the danger degree of the dangerous object of group B is higher than that of the dangerous object of group C and the danger degree of the dangerous object of group C is higher than that of the dangerous object of group D.