Using solid powder directly, an approach to acquire the fluorescence polarization is demonstrated by combining solid surface fluorimetry and fluorescence polarization, and the fluorescence polarization properties of vitamin B2 are researched with this method. The results show that the degree of fluorescence polarization of vitamin B2 solid powder is dependent on the incident angle of the exciting light, and is independent of the relative compactness when it is greater than 0.6667. The degree of polarization hits 0.4178 while the incident angle is 45°. It is 1.42 times of that the detected result from the aqueous solution. The degree of fluorescence polarization of the vitamin B2 solid sample keeps steadily in error band under constant illumination for 6 h.