Abstract:For the problem of big dispersion of nut factor,which is unfavorable for pre tightening force control,based on the one way analysis of variance theory,through the tighten experiments on different strength grade,coating thickness,rotational speed,bolt chromate treatment,bearing surface hardness of the bolts,the key factors affecting bolt friction coefficient were found out.It is shown that D chromate treatment bolts can effectively improve the tighten bolt axial force and give full play to the bolts using efficiency.Through control the key factors affecting bolt friction coefficient,the dispersion of nut factor is effectively reduced and the reliability of connector is improved.