In order to weaken the impact of external environment on the laser monitor technology，this paper analyzed the main factors which would impact the laser monitoring system.Starting from the receiver system,4QD photo detector was adopted, the relations between natural resolution and division precision was deduced from deflection angle produced by acoustic wave vibration;then by analyzing external constraints of 4QD detection system under atmospheric conditions the super advantages of the four quadrant detection system subjected to outside constraints in atmospheric environments was described. The above opinions were finally proven by designed example and test.