Investigation of gamma-channel widening behavior in a nickel-base single crystal superalloy during uniaxial tensile creep tests was carried out. Scanning electron microscopy (SEM) was adopted to reveal the microstructural evolution of gamma-channel and the dimension of gamma-channel. It was found that different tests condition such as temperature, time and stress in tensile creep tests all influenced the gamma-channel widening behavior, and a parabolic rate law governs the mean increase value of gamma-channel width. The stress and temperature enhanced the gamma-channel widening. The gamma-channel widening was the result of directionally diffusion of multiatom.