Electromagnetic environment with a high efficiency based on single device supports has wide range of applications. But the efficiency of parallel ray-casting for rendering electromagnetic environment is restricted by the device. Based on researching the restriction of device for parallel ray-casting, a pixel interpolation method focusing on the restriction was presented. The number of rays was reduced when the parallel ray-casting rendering under device restriction couldn’t be completed immediately, namely, a part of pixels in the rendering image were generated by ray-casting and the rest pixels through interpolation. Pixel interpolation got rendering efficiency at the cost of image quality, so when image update paused, the interpolated pixels were regenerated to recover image quality. The experiments show that pixel interpolation obviously improves rendering efficiency when implemented on a low device. Compared with the rendering images of some volume data and the errors in these images, the electromagnetic environment data has the best rendering result, which proves that pixels interpolation is useable especially for rendering electromagnetic environment on a low device.