分析了JB/T 4730—2005标准对两类检测技术级别的规定。应用曝光曲线、胶片特性曲线方程以及技术级别的规定，建立了几何、物理透照参数间的函数关系。讨论了同时满足JB/T 4730—2005标准规定的透照厚度比K值与黑度范围ΔD0所需的参数条件。提出一种选择射线检测参数的优化方法，并通过实验进行了验证。结果表明，应用该方法可对检测参数优化，且使标准对技术级别的规定得到满足，解决了射线检测中分立选择几何、物理透照参数存在的问题。

In regard to the problem due to respective choice of testing parameters in common radiographic testing, the requirement for two technique classes in JB/T 4730: 2005 standard is analyzed. Using exposure curve and film characteristic curve equations, together with technique classes, the function relation between geometric penetration parameters and physic penetration parameters is established. The parameter conditions in which values of penetration thickness ratio K and film density tolerance ΔD0 are satisfied simultaneously are discussed. Based on the above mentioned ones, an optimized method for choice of testing parameters is proposed, and is verified by the experiment. The results show that two technique classes in JB/T 4730: 2005 standard can be reached by the optimized method.