To study the Z-direction properties of thick plate steel, samples were extracted by different locations and directions from plate steel of different thickness and different sizes of crossing butt weld. Then the samples were supplied to simple tensile test at temperatures from -60 ℃ to 20 ℃. The principles that Z-direction property and ψ change with the thickness of the plate, the size of the weld, the difference of sampling and the difference of temperatures were analyzed. It is indicated that: fy, fu and ψ decrease with the increase of the plate thickness; fy , fu and ψ of the samples of Z-direction affected by weld are much lower than that of non-affected Z-direction, which are lower than X direction;fy and fu increase, but ψ decreases with the decrease of temperature; and the brittleness with cooling is manifested. The data of Z-direction tensile is accumulated, which can be applied in much more accurate measurement of Z-direction properties and much more rational design.