It is well known that galaxy inflow and outflow play important roles in shaping the history of galaxy evolution. However, any existing telescopes or instruments cannot directly constrain these processes in the distant universe. We here attempt to study the inflow and outflow properties of galaxies by adopting a simple model and by exploiting key observational properties (stellar mass, gas fraction, and metallicity, i.e. "integrated" properties of star formation in the past). We used 3441 local galaxies from the cross-matched SDSS-ALFALFA samples. These galaxies are divided into 24 subsamples by their stellar mass and the offsets from the star-forming main sequence (ΔMS). We fit the galaxies in each subsample (hence at fixed stellar mass and SFR) with the ’leaky-box’ model and obtain their inflow and outflow parameters. We find that, while both inflow and outflow parameters depend on ∆MS, only inflow parameters show a trend with stellar mass. In my poster, I will discuss the interpretation of our results in the context of the geometry of star formation within the galaxies as well as the shape of the gravitational potential well of the galaxies (the distribution of baryon and dark matter).