REUTERS/William Hong
Economists polled by Bloomberg are looking for manufacturing to rise to 48.3, from 48 the previous month.
A reading below 50 indicates contraction.
Chinese GDP climbed 7.4% in the first quarter, confirming the economic slowdown economist and investors have been talking about.
Policymakers have set a growth target of 7.5% for 2014, and economists expect they have a floor of 7% GDP growth for the year.
A disappointing flash PMI number will only add to concerns about a possible hard landing.