The emerging 2D material, graphene oxide (GO), provides an ideal substitute to overcome many major issues of water treatment membranes. The performance of GO membranes can be adjusted by controlling the interlayer spacing, but manipulating the interlayer spacing in subnanometer range and applying GO membranes to pressure driven filtration application remain big issues. Here, asultrathin GO membranes (50 nm) were fabricated, and diamines were used as crosslinker to control the interlayer distance and prevent GO expansion in water. XRD confirms that crosslinked GO (cGO) membrane has smaller interlayer spacing expansion (from 7.83 Å to 10.6 Å), compared with non-crosslinked GO membrane (from 7.20 Å to 13.3 Å). The water permeance of all cGO membranes are about 60% of non-crosslinked GO membranes. cGO membranes have the same low rejection for monovalent ions (Na+ and Cl-) but more than double rejection for divalent ions (Mg2+ and SO42-), which suggests that size exclusion is the predominant mechanism for salt rejection. These demonstrates that the crosslinkers successfully adjust the interlayer distance of GO membranes in subnanometer range and alleviate GO expansion in water.