"设计计算法" can be translated into English as "design calculation method" or "method of design calculation", depending on the context and specific usage.
"Design calculation method" is a more concise and commonly used phrase, directly referring to the approach or technique used in the design process for calculations.
"Method of design calculation" provides a slightly more formal or detailed expression, emphasizing that it is a specific method within the realm of design calculations.
In most cases, either expression would be appropriate, but "design calculation method" is likely to be the more frequently used term.