Abstract: The decommissioning management process of nuclear facilities requires rapid classification and detection of soil radionuclides and contamination levels, of which ⁹⁰Sr is one of the focus nuclides. Both ⁹⁰Sr and its daughter ⁹⁰Y emit only β-rays, which cannot be measured directly due to the limited capacity of β-ray penetration. The traditional method is sampling and separation. ⁹⁰Sr is separated from the soil by radiochemical process, and then ⁹⁰Sr activity is measured. This process is time-consuming and labor-intensive, cannot rapidly analyze the ⁹⁰Sr content, and in addition, generates a large amount of secondary radioactive waste. In order to solve the problem of direct measurement of ⁹⁰Sr in environmental soils, a stacked plastic scintillation fiber(SCiFi) array detector with a 5-layer structure was developed. This detector utilizes the characteristics of the difference in the energy of different β-rays as well as the difference in the interactions of different rays with matter, and combines a specific detector structure and signal analysis logic, to realize the detection of high-energy β-rays of ⁹⁰Y from γ-, β-, and cosmic-ray radiation environments, thus realizing the direct measurement of ⁹⁰Sr. The detector consists of 4 layers of 800 plastic scintillation optical fibers of 1 mm squar, and every 25 fibers are divided into a group to connect a piece of silicon photomultiplier device(SiPM) of 6 mm×6 mm, which converts the scintillation fluorescence into electrical signals, and the logical relationship between signals is processed by self-developed integrated circuit based on field programmable gate array(FPGA). For detectors with large-area flat plate structure, the variation of detection efficiency at different position is an important parameter. The detection efficiency was measured in different areas. And the minimum deviation of detection efficiency at different positions along the optical fiber length of 40 cm is 2.7%, which indicates that the effective length of the scintillation optical fiber is suitable, and detectors with larger sizes can be processed. In addition, the use of SiPM optimizes the detector structure and allows the fabrication of smaller detectors. The key performance parameters of the detector were tested. The effective detection area of the detector is 800 cm², the detection efficiency of ⁹⁰Sr in soil is 1.2%, the lower limit of detection is 0.2 Bq/g(5 min), and several real contaminated soils were measured with the same ⁹⁰Sr content, which meets the demand for direct measurement of soil ⁹⁰Sr content.