Laser indirect-drive has the potential to obtain ultra-high pressure which is very useful for shock physics. The isentropic compression can be obtained with reservoir target in laser indirect-drive experiment. The free surface velocity and interface velocity are the two important parameters in isentropic compression experiment. The efficiency with reservoir target is lower than that in the isentropic compression experiment with long pulse laser direct-drive. However, the isentropic compression experiment with long pulse in laser direct-drive is very sensitive to the laser intensity variation. In this paper, the isentropic compressions with reservoir target with indirect-drive and direct-drive on Shen Guang-Ⅲ prototype laser facility are investigated separately. And the important technique is introduced to provide the reference data in this field. And the isentropic compression with long pulse laser direct-drive is analyzed on Shen Guang-Ⅲ prototype laser facility. The interface velocity on Al/LiF is achieved with three steps. The blank effect is provided and analyzed. These data show that with long pulse in laser direct-drive, a pressure, which has been highest in China up to now, can be obtained. With these experiment data, the feasibility to do the isentropic compression experiment on Shen Guang-Ⅲ prototype laser facility has been approved.