The work aims to introduce a new type of switched Lorenz chaotic system into image encryption system to improve the effect of image encryption. When the image encryption system adopted the "scrambling-diffusion- scrambling -diffusion” process, firstly, combined with the key K, the switched Lorenz chaotic system was combined with four order Runge-Kutta equations to discretize the plain image, and the plain image matrix was scrambled through the Arnold mapping; the image was diffused through the bit "exclusive-OR" operation; and then the image was scrambled through the Logistic mapping; finally, the image was diffused through the "cyclic shift" operation. Through the simulation experiment to test the performance of image encryption, the test values of the encrypted image's related parameters NPCR and UACI were approximately 99.60 and 33.4, respectively, which were very close to the theoretical values. The information entropy test result was approximately 7.997, which was also very close to the theoretical value of 8. It is shown that the image encryption system with new switched Lorenz chaotic system has strong robustness and reliable security, and can effectively improve the anti-attack capability of the encryption system.