Aero-engine combustion chamber is a round thin-walled part comprised of outward, upright and inward walls. For the characteristic of the round thin-walled parts, the mathematical models are developed based on the critical condition of offset melting powder without support and the cladding height of single-layer. Both inward and outward thin-walled parts are investigated for the offset value, forming height and angle of inclination. The results show that, due to the difference of geometry the inward thin-walled parts have longer offset, higher forming height and bigger slope angle than those of outward thin-walled parts under equal offset condition. The simulated parts of aero-engine combustion chamber are formed in the experiment. The results provide further understanding for laser forming round thin-walled parts both in theory and application.