The FEM model for calculating friction heat generation of piston group was built and the required kinematics and dynamics conditions were achieved by the calculation of engine working process. Taking a 12cylinder turbocharged diesel engine as the research object, the variations of transient friction force and transient heat generation power with crank angle at rated conditions were calculated, total power of friction heat generation for piston group and its distribution in piston ring, piston skirt and cylinder liner were acquired, the temperaturerising phenomenon resulted by piston friction was determined and the influences of speed and load on piston group friction heat generation were analyzed.