Random changes of atmospheric turbulence have restrictions on the performance of satellite-to-ground laser communication. High-speed laser communication proposes new requirements on the description of turbulence characteristics in a short period. A direct, real-time measurement of atmospheric coherent length method based on lateral shearing interferometry is proposed. By measuring the sheared phase distribution of the phase distortion caused by atmospheric turbulence, considering that the time average of phase structure function is equal to the ensemble average when the turbulence is an ergodic random process and combining the Fried phase structure function, the atmospheric coherent length can be measured. Experiments are conducted by using a 635 nm laser wave through a 1.2 km distance. The results demonstrate the feasibility of this method, and solve the constraints in time accumulation and statistical analysis of the traditional measurements.