Today, the importance of fintechs in the financial field is not hidden from anyone. The importance of this matter is to the extent that a wide range of recent studies have been conducted on the performance of fintechs and their relationship with the banking sector at the international literature. In Iran, there are more than 50 fintech companies that have entered into various sectors of the banks' business model. Therefore, they can affect the financial stability of the Iranian banks. In this article, using data of fintechs and financial statement of banks during 1991-2021 and ARDL and Quantile methodology, the effect of fintechs in the short and long term on the financial stability of banks has been investigated according to the type of ownership, the size of the banks, and the degree of financial stability. In this article, fintechs are divided into two groups: competing fintechs and non-competing fintechs. Fintech lifetime has been used as a measure of fintech performance. The z-score has been used as a measure of financial stability of banks. The results of the accuracy of the model indicate the normality of the distribution of residual sentences, the absence of serial correlation, the existence of homogeneity variance and the existence of long-term relationship. The results of the survey show a significant relationship between fintechs and financial stability of banks. So in long term, both competing and non-competing fintechs have a negative effect on the financial stability of banks. But in the short term, non-competing fintechs have a positive relationship and competing fintechs have a negative relationship with the financial stability of banks. Also, examining the effect of fintechs according to the type of ownership and size indicates the negative effect of fintechs based on the type of ownership and size, and examining the effect of fintechs according to the degree of financial stability indicates the negative effect of fintechs on banks with low financial stability.