To control the radiation characteristics of random laser effectively, the random medium nano-cluster was put in a photonic crystal(PC). The finite difference time domain(FDTD) method was used to simulate its radiation characteristics after it was placed in the air and in the PC. The results show that if the cluster is put in the air, the radiation energy decreases gradually after being excited, and its emission spectra take on spontaneous emission characteristics. However, when the cluster is introduced into a PC, some spontaneous emission spectral peaks will drop off, one of which will leave and grow in intensity rapidly. Finally, it becomes the strongest single spectral peak. Therefore, if a random gain system is able to be put into a matching ordered system, the light can be confined and the spontaneous emission can be forbidden.