The influences of some additives such as dissolving promoters, plasticizers and molecular stabilizers of polyacrylamide sizes on the adhesion of the sizes to polyester and cotton fibers were investigated for warp sizing. The additives evaluated included glycerine, sodium sulfate,sodium nitrite, urea, thiourea, and sodium dodecyl benzene sulfonate. By an impregnated roving method, the adhesion was evaluated in terms of the maximum strength and work to break of slightly sized roving. The polyacrylamide used was prepared through solution polymerization by free radical initiator. It was found that the variation in the adhesion depends not only on the type and amount of additives, but also on the fibers to be glued. Some additives improve the adhesion while others can not. To enhance the adhesion,sodium sulfate is superior to urea or sodium dodecyl benzene sulfonate as dissolving promoters; sodium nitrite is better than urea as plasticizers; and glycerine is favorable to urea and thiourea as molecule stabilizer. Moreover, the experimental results are also discussed and analyzed from the viewpoint of adhesion theory, especially in accordance with the weak boundary layer and internal stress on the interfaces of fiber-adhesive layer.