In order to explore the influence of manufactured sand dosage on the flexural performance of self-compacting lightweight aggregate concrete beams (SCLC), five SCLC with 0%, 30%, 60%, 80% and 100% manufactured sand dosage for four-point bending tests. The deflection curve, mid-span deflection and crack distribution of SCLC beams with different manufactured sand dosages under load were studied, and the influence of manufactured sand dosage on its cracking moment and flexural capacity was explored. The results show that the average strain of each test beam section conforms to the plane section assumption, and the load-deflection curves are basically similar. With the increase of manufactured sand dosage, the SCLC beam has more secondary cracks and more uniform crack distribution. The maximum crack width decreases under the same load before yielding. The mid-span deflection and ultimate bearing capacity reach the maximum when the manufactured sand dosage was 80%, which were increased by 16.13% and 6.62% respectively compared with SCLC beams with all river sand. Utilising the deflection calculation formula of lightweight aggregate concrete, the deflection calculation value of each test beam differs from the test value. The cracking moment of the test beam was calculated using the standard formula, and the calculated value is quite different from the test value. Through the analysis of test results and calculation of flexural bearing capacity, it can be concluded that the optimal dosage of manufactured sand in SCLC is 60%-80%.