The invention discloses a fly ash non-burned high-strength ceramsite and a preparation method thereof, wherein the ceramsite comprises the following components in parts by weight: 93.5-94.5 parts of fly ash, 2.95-3.05 parts of an adhesive, and 2.95-3.05 parts of an enhancer. The method comprises the steps: preparing an adhesive liquid and an enhancement liquid respectively from the adhesive and the enhancer with water; pouring the weighed fly ash into a ball formation disc, starting up the ball formation disc, spraying the adhesive liquid into the fly ash, rotating the ball formation disc, and rolling to form balls; at the same time, spraying the enhancement liquid to the surface of formed ball bodies to prepare ceramsite; and putting the ceramsite into a steam curing kiln, curing for 8-9 h, and thus obtaining the product. A sintering process is not required, and the high-strength ceramsite can be obtained; tests verify that the prepared fly ash ceramsite has the packing density of 800-900 kg/m<3>, the cylinder compressive strength of 7-8 MPa and the water-absorbing rate of less than or equal to 15% and has good quality.