OBJECTIVE: To evaluate the technical level and ability of the detection of free silica in dust in occupational health technical service institutions of Guangdong Province through inter-laboratory comparison. METHODS: The interlaboratory detection of free silica in dust in 55,61,58 and 66 occupational health technical service institutions were carried out and compared in 2012-2015. The results were statistically analyzed by four points robust statistical technique,and the relative deviation between the laboratory test results and the Median of them was used as the auxiliary evaluation index of the laboratory's technical ability. RESULTS: The stable coefficient of variation(CV) of samples with free silica content > 20. 00% was less than 5. 00%,and the stable CV of samples with free silica content ≤20. 00% was more than5. 00%. The qualified rate in 2012-2015 were 89. 09%,81. 97%,77. 59% and 81. 82%,respectively. There was no statistical difference(P > 0. 05) in the annual reference between private and non-private institutions compared to the qualified rate in 2012-2015. There was no statistical difference(P > 0. 05) in the qualified rate of the institutions in the Pearl River Delta region and in the non-triangular regions of the Pearl River Delta in 2012-2015. CONCLUSION: Comparison of the detection technology service ability in the detection of free silica in dust should be conducted to improve its technical service quality.