1. A method of reducing computation of water tolerance by projecting touch data, the method comprising steps of: obtaining capacitance raw data of a sensing array having row sensing lines and column sensing lines; comparing the capacitance raw data with reference raw data to obtain a difference array; obtaining a row projection list by extracting minimum values of rows the difference array; and obtaining a column project list by extracting minimum values of columns of the difference array; determining at least one rectangular water block by the row projection list and the column projection list; preventing dynamic calibration on the at least one rectangular water block; wherein the step of determining at least one rectangular water block by the row projection list and the column projection list is to compare the row projection list with a first water threshold and compare the column projection list with a second water threshold respectively to form a row water mask and a column water mask to determine an extent of the at least one rectangular water block, and wherein if a number of adjoined row sensing lines in the at least one rectangular water block is greater than a row-threshold and a number of adjoined column sensing lines in the at least one rectangular water block is greater than a column-threshold, sensed signals generated in the at least one rectangular water block are filtered out or neglected.