Starting from the energy necessary for atomic ionization and plasma maintaining, a method is developed to estimate the required energy and implosion velocity for a material to emit a certain shell X-ray radiation in a Z-pinch. The typical load current and voltage in Z-pinch process on “Qiang Guang-I” generator are analyzed to obtain the inductance and the work done by Lorentz force, as well as the effect of load parameters on them. The inductance is not in good agreements with that calculated from the theory based on the shell model of Z-pinch, possibly due to the over simplification of the model and the measurement limitations, such as the measuring points of the current and voltage are always several centimeters away from the load. It is found in the experiments that the inductance increases with the load current until the end of the X-ray radiation pulse, and is saturated at ～100nH. The work done by Lorentz force is maximal when the diameter of tungsten wire array is 8 mm in our experiments. The work done to the load with more wires is greater than that to the load with less wires if the diameters of the wire arrays are the same, say 8 or 10 mm. At the same time, the calculation for optimized masses per unit length of gas-puff and wire array load was carried out for the “Qiang Guang-I” generator on 1.6MA current level. The optimized results show that the tungsten wire array with 8 mm diameter should be the best load for this generator. This is consistent with the experimental result on the “Qiang Guang-I”.