A construction for loosing prevention and position fixing of rule tape of tape ruler comprises a main housing having a handle formed at its upper end, and a wound rule tape for measurement is installed in the main housing. The free end of said rule tape is attached with a buckle ring and there is installed with a magnetic element adjacent to said buckle, so as to absorb said buckle ring be located at a fix position and prevent the generation of pulling force due to the weight of buckle ring, the rule tape then would not be loosen; in addition, there is a fixing element installed in the main housing, in measuring the distance between two objects, the fixing element is taken apart off main housing in advance, and then the fixing element is stickled into a position to be measured, afterwards, the buckle ring at the free end of rule tape is mounted onto the fixing element to fix the end of rule tape at a designated position. Thus the measurement can be achieved by only one people.