The beta effects on the plasma equilibrium in Modified Bumby Torus (MBT) sector, which is an asymmetric closed line system with l=0 and fairly large l=+or-1 field distortions, are studied. For this purpose, the equilibrium of high beta plasma produced by theta-pinch is compared with that of betaless plasma numerically calculated from the measured magnetic field profiles in device. The equilibrium condition depends weakly on beta value, but the plasma cross-section is vertically elongated as the beta value increases. The m=1 long wavelength MHD instability is not observed during the observation time of approximately 15 mu s. These experimental results are compared with MHD theory based on the new ordering taking the finiteness of l=+or-1 field distortion ( delta +or-1>or approximately=1) into account, which suggest significant stabilizing effects due to self formation of magnetic well and also due to the conducting wall.