In this paper, we discuss the problem of the local energy content in gravitational fields. A new total energy-momentum density pseudo-tensor of gravitational field is given In this paper. The energy content in any part of a gravitational field given by the new pseudo-tensor is an invariant under arbitrary purely spatial transformation, hence the local energy content in the gravitational field has a well-defined physical meaning. For the energy and momentum of a Schwarzschild gravitational field, the results given by the new pseudo-tensor are more reasonable than those given by other pseudo-tensors pro-posed in the literatures of the general theory of relativity.The relation between mass and energy in the theory of gravitation is also discussed.