In this study, soil-geocell interaction behavior was investigated by using the large scale laboratory pullout test box. The large scale pullout box (1500 mm length, 1000 mm wide and 700 mm height) was designed and built to determine the behavior of the soil-geocell interaction. A total of 18 pullout tests were conducted under 10, 25 and 50 kPa vertical uniform pressure. The soil used in this study was poorly graded sand with specific gravity (G(s)) of 2.67, the average particle size (D-50) of 1.6 mm, maximum and minimum void ratios were 0.79 and 0.43, correspondingly. The maximum and minimum dry unit weights of the sand were found to be 14.52 and 18.10 kN/m(3). The model pullout tests were performed at relative densities of 50%. The internal friction angle of the sand at relative density of 50% determined from direct shear tests was 39 degrees. The displacements and deformations were measured to obtain the distribution of stress on the geocell. The results show that the displacements and deformations reach higher values at the near of front wall of the test box. In this study, as we expected that increase in vertical load results in increase in the pullout forces. Within the scope of this study, the variation of the SxL (cell number x length) parameter, which is expressed to determine the effect of the dimensions of geocell elements on the pulling force, on pullout forces is determined. It is concluded that there is a correlation between values of SxL and pullout forces in soils. Moreover, pullout interaction factor for geocells reinforcement decrease with increasing normal pressure.