Processlist show most of the queries are sending data for select query

I have faced some problem like sending data state in processlist. In my application I used parallel processing which send 50 count at a time, and that will do some MySQL database operation (select and insert), but after few minutes nothing happened. Then I see in database with SHOW PROCESSLIST; most of the query is in SENDING DATA state with 1001 threads. my max query size is 1000. I decrease the size 50 to 10 but no luck. Can anyone suggest me how to solve this problem.