A method for manufacturing an isolating layer onto a crucible includes the steps as follows: providing a spraying device for the following spraying steps; heating the crucible and measuring the heated crucible to get a first temperature; spraying a slurry on the inner wall of the crucible to form an isolating layer by a spraying unit with a predetermined spraying manner; measuring the isolating layer to get a second temperature; obtaining a value for the difference between the first and second temperatures and judging whether the difference value in a within predetermined difference scope or not, in which the predetermined difference scope is about 6° C.˜12° C.; when the difference value is not in the predetermined difference scope, adjusting the predetermined spraying manner; when the difference value is in the predetermined difference scope, implementing the above spraying steps to the crucible.