Based on China’s provincial data from 1978 to 2011, we use CES production function with general factor-augmenting technical progress to estimate aggregate and sectoral elasticity of substitution series by variable parameter panel data model. Then we evaluate two kinds of Solow’s conjectures by empirical investigation. The main findings are: both AES and SES are significantly below unity, so CD aggregate production function is rejected in China; consistent with some recent empirical findings, China’s AES shows an increasing trend in the Reform period, which strongly supporting Solow’s conjecture 1; meanwhile AES is clearly lower than the weighted average of SES, and Solow’s conjecture 2 can be rejected. In the end, an outlook for future research is proposed.