The role of weak adsorptive polymer chains in the colloidal particles solution is studied by self-consistent field theory (SCFT). The numerical results show the potential between colloids are attractive interaction. Besides the depletion effects the chain conformations such as loop, tail and bridge between two spherical colloidal particles play important roles. The quantitative polymer concentration dependent chain conformations and then the effective potential are also addressed. (c) 2012 Elsevier Ltd. All rights reserved.