Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) has successfully started in-orbit operation. The results of the ground tests and in-orbit performance measurements are described and compared in this paper. We found that the in-orbit performance is fully satisfy the specifications and SMILES data has sufficient quality for atmospheric science study. The system noise temperature in orbit is consistent with that measured in the ground test if the result of the ground test is modified correctly. The measured System noise temperature measurement is also influenced by the receiver gain nonlinearity. There is still a room for improvements, for example nonlinearity correction, in Level 1B processing of SMILES.