In addition to the object reflective property at the laser wavelength, the echo intensity data acquired by terrestrial laser scanner is also related to other factors，which reduces the reliability and accuracy of object classification based on intensity data. The effects of instrument, distance, incidence angle, object reflector, and environmental conditions on intensity data are studied with Leica ScanStation2 laser scanner. The results indicate that with the increasing of distance, the intensity value increases at first and then decreases, and the maximum value occurs at about 15 m, while its standard deviation declines oscillatorily and tends to be stable after increasing to 55 m. The effect of incidence angle on intensity data is related to object properties, such as object reflectance at the laser wavelength and homogeneity. Colors close to laser wavelength and the color of laser itself generate higher intensity values, while introduce higher standard deviations. For the same object, the intensity value in dry condition is greater than that in wet condition. Environmental conditions have no significant impact on intensity value.