Active triangular focusing method has received wide attention because of its advantages of simple structure,fast test speed,convenient and flexible use,and etc. It has great application value in fields such as automated production and industrial measurement. However,there is a potential loss of target in the face of small objects being measured or objects with unconventional surfaces such as large curvature. In response to this problem,considering the LED has large illumination field of view,an active triangular focusing method for small targets based on LED is proposed. The method is verified to measure the distance of small targets and unconventional surface objects from both theoretical and experimental aspects. The experimental results show that the actual test value of the model is basically consistent with the theoretical analysis value,which proves the practicability of the model and broadens the application range of laser triangulation ranging technology.