"用实验方法" can be translated into English as "by experimental means" or "using experimental methods".
Both expressions are commonly used in scientific and academic contexts to convey the idea of conducting research or investigations through experiments. For example:
"We verified this theory by experimental means."（我们用实验方法验证了这个理论。）
"The researchers are using experimental methods to study the effects of the new drug."（研究人员正在用实验方法研究这种新药的效果。）