With two new tortoise coordinate transformations, Hawking effect from a dynamical Kinnersley black hole is investigated by using the improved Damour-Ruffini method. After the tortoise coordinate transformation, the Klein-Gordon equation can be written in the standard form at the event horizon. Then extending the outgoing wave from outside to inside of the horizon analytically, the surface gravity and the Hawking temperature can be obtained automatically. It is found that Hawking temperature of different points on the surface are different. There is a problem of dimension in the usual tortoise coordinate and the results are different from those of the same black hole by using two different tortoise coordinate transformations. The results obtained by using two new tortoise coordinate transformations are still different.