A novel jacket with circumferential parallel minichannels was proposed, and numerical simulation on the heat transfer characteristics of the jacket was carried out. The effects of mass flow rate, size and number of channels on the heat transfer were examined, which was compared with the jacket without minichannels. The results indicate that the average temperature and temperature inequalization coefficient of inner cylinder wall in the jacket with minichannels are 9.7 K and 36.7% lower on average than those of the jacked without minichannels in research scope, respectively, and both decrease with the increase of mass flow rate. Under a given height of minichannel, the smaller the width of minichannel, leading to more minichannels, the lower the average temperature of inner cylinder wall, but the temperature inequalization coefficient is almost constant. The more the minichannels of jacket, the more uniform the temperature on the same cross section, and the temperature inequalization coefficient reaches a constant value with the increase of mass flow rate. The average heat transfer coefficient of the jacket with minichannels is 0.87~2.04 times of that of the jacket without minichannels, which increases with the increase of number of minichannels. The coefficient rises with the increase of mass flow rate, but when the flow rate reaches a certain extent, the incremental rate of the coefficient is gentle, and the more the minichannels, the gentler the incremental rate. Based on the simulation data, the average Nusselt number can be expressed as Nuave=3.71696Re0.30341(Dh/Rc)0.28574.