Abstract: Round-section specimens instead of plate specimens which were sampled from different position and direction out of three thickness 9Ni3CrMoV plate steels of 36mm, 50mm and 80mm were prepared to measure the tensive flow behaivor．The work hardening exponents（n value） were calculated out of the obtained curves, and the influence of sampling position and direction on n value was investigated．The results indicate that the sampling position and direction have little effect on n value．The n value is linearly proportional to σ_s／σ_b or σ_s．Under the maxium load,the true strain or ε_b of 9Ni3CrMoV steel is less than n value, and their quantitative difference is within 10 percent．