This paper describes the theory and method of the mobile phone combined with rangefinder instead of the traditional log scaling.Based on the distance data measured by the image and rangefinder instrument,computer vision technology is used to segment the end face of wood and the photogrammetry technology used to calculate face area and the volume.The example analysis shows that the measurement accuracy of this method and the manual measurement error is less than 3% and meets the national requirements for wood scale error,but for some enterprises which require less than 1%,it has not met their error requirements.The method can replace the traditional timber inspection ruler,improve the working efficiency of the workers and reduce the risk of the work.