China's major property developers' profits are falling due to rising operational, labor and raw material costs, according to an industry study.

Despite fast-growing property sales last year, average net profits of the country's top 500 developers stood at 434 million yuan ($68.9 million) in 2012, down 18.64 percent year-on-year, according to the study conducted by the China Real Estate Research Institute, China Real Estate Association and China Real Estate Valuation Center.

The average return on assets for the top 500 developers was 2.15 percent for 2012, compared with 33.31 percent for 2011. Their average rate of return on common stockholders' equity was down 39.88 percent year-on-year to 4.7 percent.

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