This paper numerically investigated the influences of pin-fin size and layout on the flow characteristics of cooling air in the trailing edge of a real low pressure turbine blade. The discussion was given first for the baseline model without pin fins (denoted as M0) under a turbine design condition and two off design conditions. Then a comparison of the flow fields in the turbine blade especially in the trailing edge region was performed with three more trailing edge models, with the purpose of discovering the benefits of using pin fin configurations in a real low pressure turbine blade. The other three models (denoted as M1, M2, M3) have pin fins in different diameters and arrangements. The M1 model has a row of 13 pin fins with a diameter of 2mm, and the M2 and M3 models have two rows of pin fins arranged in a staggered pattern with a diameter of 1.2mm. Compared to the baseline model M0, it is shown that an addition of pin fin configurations helps greatly to improve cooling flow distributions and to mitigate the blockage of coolant in trailing slots. Meanwhile, the adoption of pin fins has not only affected significantly the flow field in the trailing passage but also has moderately affected flow fields in the middle and forward cooling passages. Increasing pressure ratio can increase total mass flow rate with no significant change in flow patterns. The baseline blade Model M0 shows a high value of 6 for a friction loss related performance function at the turbine design condition. However, only a moderate increase in the value of the performance function is discovered for all the three blades with pin fins.