For a rotating machine with one or more tilting pad journal bearings (TPJBs), it is acommon state that pad-to-journal assembling clearances are uneven in one bearing, or inconsis-tent relationship of assembling clearances are encountered among all the bearings. Consideringthe structural characteristics of a TPJB, a concept named as “pad pair pre-load coefficient” corre-sponding to bearing pre-load coefficient is proposed. Firstly, the influence of bearing pre-load coef-ficient and pad pair pre-load coefficient on shaft vibration in a Jeffcot rotor is analyzed. Then takingNo.1 unit with two TPJBs in Guangzhou pumped storage power plant (GPSP) as an example, theinfluence of inconsistent relationship of the two bearing pre-load coefficients on shaft vibration isanalyzed. The results show that variety of one bearing pre-load coefficient will only influence vibra-tion amplitude, not involving the shape of shaft center orbit. But variety of one or more “pad pairpre-load coefficient” will influence not only vibration amplitude, but also the shape of orbit-whichwill be turned from a circle to an ellipse. By investigating variation characteristics of shape andvibration amplitude of orbits at the TPJBs, some theoretical bases will be supplied for diagnosingthe condition of the unit bearings. For a rotating machine with one or more tilting pad journal bearings (TPJBs), it is acommon state that pad-to-journal assembling clearances are uneven among one bearings, or inconsis-tent relationship of assembling clearances are encountered among all bearings. structural characteristics of a TPJB, a concept named as “pad pair pre-load coefficient ” corre-sponding to bearing pre-load coefficient is proposed. First, the influence of bearing pre-load coef-ficient and pad pair pre-load coefficient on shaft vibration in a Jeffcot rotor is analyzed. Then taking No. 1 unit with two TPJBs in Guangzhou pumped storage power plant (GPSP) as an example, the inluence of inconsistent relationship of the two bearing pre-load coefficients on shaft vibration isanalyzed. results show that variety of one bearing pre-load coefficient will only influence vibra-tion amplitude, not involving the shape of shaft center orbit. But variety of one or more “pad pair pre-load coefficient” affect not only vibration amplitude, but also the shape of orbit-whichwill be turned from a circle to an ellipse. By investigating variation characteristics of shape and vibration amplitude of orbits at the TPJBs, some specific bases will be supplied for diagnosing the condition of the unit bearings .