@Lan, you could do this by using TapTarget for Marketo (see taptarget.com/marketo). TapTarget is a mobile marketing automation platform, this means you integrate a small snipped of code in your app, and TapTarget will then start capturing app activity in your app and send it to Marketo.
You can choose what to capture, for example only fields that have been filled out in your native mobile app. TapTarget will sync these fields to Marketo, creating new leads or merging with your existing leads.
Best,
Niko