A well-established side-suspended maglev rotating system possesses two permanent magnet guidways (PMGs) with unimodal magnetic field for every one of them. The maglev vehicle of the system can reach a speed over 80 Km/h at the suspending gap of 6 mm in an evacuated circular tube. A way to increase the maximum speed of the system without changing the whole structure greatly is discussed. Putting the two parallel PMGs together to form a single PMG with trimodal magnetic field will obviously increase levitation force of the system. This will be possible to increase the maximum speed of the system. However the mass of vehicle will increase at the same time to contract the effect of the increase of levitation force. Evaluating the effects of them generally indicates that the trimodal structure PMG (TMG) can support higher speed than that of the unimodal structure PMG (UMG). Otherwise, maximum speed for TMG augments with the increase of the number of bulks. When the number of columns of bulks is 17, the speed for TMG is 8.2 percent larger than that for UMG.