Abstract: X-ray detector has experienced gas detector and scintillator detector, and entered the era of semiconductor detector. As a new type of semiconductor detector, silicon pixel detector has the characteristics of high resolution, high detection efficiency, fast time response and low power consumption. In order to study the detection efficiency of silicon pixel detector, an X-ray detection system was designed and experimental research was conducted. Four kinds of X-ray energy 4.51 keV, 5.41 keV, 6.4 keV and 8.05 keV were tested. After error analysis and data processing, the detection efficiency of frontal incidence was 53.00%, 51.56%, 40.65% and 29.91%, respectively. This experimental study provides a new approach for finding high detection efficiency X-ray detector.