Abstract: With the analysis on the structure features of the two-leg hydraulic powered support and four-leg hydroulic powered support, the paper studied the loadin g features of the two leg powered supports with different resistances and the two leg and four-leg powered supports with the same resistances as well as the factors aff ected to the loading features of the powered supports. Also the paper had an analysis on the suitability of the powered supports. The study held that the structure featur es of the powered support decided the loading features and the balance jack mechanism of the two leg powered support decided the effective loading scope near the m ain roof support bottom, and the ability of the two-leg shields to contral the roof can be increased by raising the capacity of the hydraulic cylinder and balancing cylinde r, but the way of balancing cylinder enhance to increase capacity of shields was limited. The articulated location between the two row legs and canopy of the four-leg po wered support decided the effective loading scope same to the leg row distance, to increase front leg resistance and to reduce the rear leg resistance could improve the support capacity at the front section of the support canopy and could make the effective loading scope forward. The loading features of the powered support decided th e suitability. The balance jack could timely adjust the loading role location above the powered support canopy and could be suitable to the general fully mechanized top coal caving mining face. The roof loading location above the high mining height fully mechanized top coal caving mining face in ultra thick seam would be multi varied b y the influences of the top coal caved and could cause the failure of the balance jack. The wider effective loading scope of the four-leg powered support could make the suitability.