Yes, the audio player supports a wide range of audio formats including the lossless one called FLAC. As you can see below, the FLAC format is displayed in the supported list of audio files.
Multi-format playback: .CDA, .AAC, .AC3, .APE, .DTS, .FLAC, .IT, .MIDI, .MO3, .MOD, .M4A, .M4B, .MP1, .MP2, .MP3, .MPC, .MTM, .OFR, .OGG, .OPUS, .RMI, .S3M, .SPX, .TAK, .TTA, .UMX, .WAV, .WMA, .WV, .XM, .DSF, .DFF
For more information, access the official website: http://www.aimp.ru/index.php?do=features