Abstract: Matrix certified reference materials (CRMs) play a crucial role in validating analytical methods and ensuring quality control. To enhance the accuracy and reliability of risk assessments for plant growth regulators, we have developed a certified reference material (CRM) for forchlorfenuron in cucumber powder, thereby improving the measurement quality of forchlorfenuron residues in cucumbers. The CRM was prepared through processes including pulping, drug-adding, homogenization, freeze-drying, grinding, sieving, mixing, and encapsulation. The liquid chromatography-tandem isotope dilution mass spectrometry (ID-LC/MS/MS) method was optimized and established for the quantification of the CRM. The certified value of forchlorfenuron in cucumber powder was determined to be 14.7 mg/kg with an expanded uncertainty of 2.7 mg/kg (k=2). Furthermore, the homogeneity of the material was assessed, along with its long-term stability at −20°C over nine months and short-term stability at 40°C over nine days. The study comprehensively evaluated uncertainties introduced by characterization, homogeneity, and stability assessments.