The cast iron cylinder liners without microhole and the cast iron cylinder liners with microhole were selected and paired with Cu-Sn/Cr coating piston rings respectively.The friction and wear tests were carried out on a reciprocating friction and wear tester.The effect of microhole on the surface of cast iron cylinder liner on the friction performance of Cu-Sn/Cr coating piston ring under heavy duty conditions was investigated by measuring the friction coefficient and wear loss of the matching pairs and analyzing the surface morphology and chemical elements before and after wear.Results show that compared with cylinder liners without microhole,the cylinder liner with microhole can reduced the friction coefficient of the matching pairs,the piston ring wear loss and the cylinder liner wear loss by 405%,5225% and 850% respectively.The microhole on the surface of the cylinder liner can provide embedded points for the Cu-Sn coating that falling off the surface of the piston ring,so that the Cu-Sn coating can play a role of secondary lubrication,which prolongs the service life of Cu-Sn coating,and reduces the friction coefficient and wear loss of the matching pairs.