This research was carried out to examine morphological changes and the feeding behavior of peacock eel (Macrognathus siamensis) at the larval stage. Fish was stocked in nylon lining tank 10 m2 at a density of 300 fish/m2. Water supply from natural pond was fertilized to create natural food. Fish samples were collected daily for analyzing of food composition and quantity beside th e observation of morphological changes. The results showed that mouth size of peacock eel larvae was 0.44 ±0. 05 mm in the thir d day after hatch (DAH). Peacock eel larvae had carnivorous feeding habit (Li/Ltth  day onwards, external morphology of the peacock eel was nearly the same as adult fish. Peacock eel from 3th day to 5th day chose nauplius to feed on. From the 6th day to the 8th day, fish chose rotifera. Peacock eel chose cladocera and copepoda from the 9th day to the 23th day. From the 24th day onwards, fish can feed on blood worms. There was no selected phytoplankton for feeding.