Elliptic paraboloid model is established, and three-dimensional finite-difference time-domain method has been employed to simulate the field distribution of discontinuous crack with different shapes and positions in fused silica output subsurface under 355 nm laser incidence. Results show that both electric field intensity and the number of enhanced points (with |E| 2.0 V/m) follow a trend of first increasing and then decreasing with the increase of collinear axis length of ellipsoid. The light intensity enhancement factor reaches a maximal value when the axial ratio is 1.1 to 1.2. If parallel collinear axis length of ellipsoid increases, the electric field intensity first increases gradually, and then becomes stable when the axial ratio is 0.53. At the same time, the number of enhanced points grows rapidly.