Shellfish fry cultivation device in upward flow sand bed and using method of shellfish fry cultivation device

The invention discloses a shellfish fry cultivation device in an upward flow sand bed. The shellfish fry cultivation device in the upward flow sand bed comprises a fry cultivation pool, a water inletpipe I, a water outlet pipe, a main water pipe and a plurality of branch water pipes, wherein the main water pipe is laid at the bottom of the fry cultivation pool; the tail end of the main water pipeis closed, the front end of the main water pipe is communicated with the water inlet pipe I, the branch water pipes are positioned on the left side and the right side of the main water pipe, the tailend of each branch water pipe is closed, the front end of each branch water pipe is communicated with the main water pipe, and a water outlet hole is formed in each branch water pipe; a sand layer islaid on the bottom of the fry cultivation pool, and a coarse sand layer, a fine sand layer and a silt layer are sequentially arranged above the sand layer; a drainage hole is formed in the middle ofthe bottom of the pool, the b