Maintaining reasonable ecological flow in the river to meet the needs of aquatic habitats is an important guarantee for the health of its ecosystem. In this paper

the middle and lower reaches of the Lancang River is selected as the study area

and the river priority conservation species fishes assessment method is constructed based on three dimensions of risk coefficient

disturbance coefficient and value coefficient

then the priority protected fishes in this area are identified. Based on Instream Flow Incremental Methodology

hydraulic habitat suitability index and high/medium/low suitable proportion were selected as habitat suitability assessment indicators

and the relationship curve between them and the flow was established to study the suitable ecological flow of priority protected fishes in spawning and adulthood. The results show that: 1) the fish with the highest priority protection level in the middle and lower reaches of the Lancang River is

Tor sinensis

2) the optimum ecological flows of

Tor sinensis

in the spawning and adult stages are

2 100 m

3

/s

and 1 200

m

3

/s respectively

and the suitable ecological flow ranges are

1 700~3 300 m

3

/s

and

800~1 500 m

3

/s

respectively

the results are between good and maximum levels of the Tennant method.