A scale is a standardized measurement tool composed of multiple items, which aims to reveal the level of theoretical variables that are not suitable for measurement with direct methods, such as beliefs, motivations, states, expectations and needs. In medical research, some disease states cannot be accurately measured, such as pain, psychological depression, cognitive impairment, quality of life and self-care ability, etc. At this time, the scale can indirectly evaluate these states by measuring some characteristics. The development process of the scale is complicated. Different from the general questionnaire, the questionnaire can contain completely different contents. However, the scale uses multiple items to describe the same characteristics of the research object from different aspects. Each item must be related to each other or aimed at the same measurement problem. The scale has the characteristics of strict compilation process, long compilation time, reliability and validity test, quantitative judgment standard, and widely recognized. The scale needs to be carefully compiled under the theoretical guidance of the core problem to be measured. Some items can not be pieced together at will to form a scale. The basic steps and methods of scale development are as follows.