A gonioreflectometer which concentrated on absolute measurement of diffuse reflection standards’ bidirectional reflectance factor (BRF) is described. The instrument employs a specially built integrating sphere as a light source and a mechanically simple, radiometrically stable filter trap radiometer as a detector. Analysis of its initial performance in 630 nm shows that the combined standard uncertainty of the measurement is 0.87 % (k=2). The hemispherical reflectance factor is obtained through integration of BRF measurement results, and it is 0.57% higher than the results scaled in National Institute of Metrology (NIM) using integrating sphere method. The difference is within the uncertainty of the two measurements, and it can validate the accuracy of absolute measurement.