Abstract: On September 11th 2009, it was found that leakage of oil cooler of turbine guide bearing at unit No. 4 of Lianhua hydropower station occurred. During treatment, to protect the clearance of turbine guide bearing segments and not to discharge by tailrace spiral case, central positioning in the turbine pit was adopted. In this way, technique improvement and higher efficiency were achieved. Further, the cause reasons of leakage were analyzed.