Background: The first important issue underlying any organization is its structure. Among structural factors, complexity, formalization and centralization are more important than others and are considered as main factors.

 The main purpose of this research is determining structural factors(compelexity, formalization and centralization ) and the preferred structure with a mechanic and organic approach in General hospitals of Yazd.

 Methods: In this research, 263 personnel at 8 General hospitals were selected by stratified Random sampling.The Standard questionnaire of preferred structure design by Veiga and Yanouzas and a questionnaire by Stephen Rabinz for determining complexity, formalization and centralization were used for data collection . Collected data were then analyzed both descriptively and inferentially l(Binomial Test and ANOVA) by SPSS software version 19^th.

 Results: The result of the research showed the personnel's complexity and formalization average scores in hospitals as above and centralization score as moderate . Also the staff preferred mechanic structure in desired status.(p=0/001)

 Conclusion:All in all we can achieve a preferred structure with changing in elements of structural factors. However, presenting a fixed and specific structure for hospitals is impossible. Therefore we must create contingency structure for hospitals to be suitable for future changes.