Abstract Studies of excited state multiple proton transfer (ESMPT) are paramount importance for both biological systems and chemical reactions while its mechanism in a controllable manner has been long sought. For this purpose, we conducted a theoretical study on the ESMPT mechanisms of 1-H-pyrrolo[3,2-h]quinoline (PQ) connecting different number methanol (MeOH) molecules (PQ-(MeOH)n=1,2). The results show that the ESMPT process can occur for PQ-(MeOH)n=1,2 complexes and MeOH molecules can effectively regulate the proton transfer barriers. The non-fluorescence of PQ-MeOH was explained by the combination of rapid ESMPT and following intersystem crossing (ISC) processes. The observed fluorescence of PQ-(MeOH)2 was owing to the contribution of increased excited-state barriers to emission is greater than the consumption of ISC process. These exciting findings revealed the cooperation mechanism between ESMPT and ISC processes for PQ-(MeOH), whereas the competitive mechanism for PQ-(MeOH)2. Our work firstly implemented the bidirectional regulation of the ESMPT mechanism, which will open new avenues for improving the luminescence properties and characterizing the cluster structure.