In practical processing, polymer melt generally experiences flow and pressure fields simultaneously, but unfortunately, in the past decades, most studies concerned about the separated effects of flow and pressure on polymer crystallization, because of the grand challenges, such as, detecting structure, implementation of shearing, dynamic sealing, etc. For this reason, we provided an insight into the crystallization behavior and crystalline morphology and structure of isotactic polypropylene (iPP) obtained under the combination of flow (0 − 9.1 s−1) and high pressure (100 MPa) by using self-designed pressurizing and shearing device (PSD), which was equipped with well-designed dynamic sealing structure and successfully solved the problem of melt leaking under high pressure and shearing. A strong shear rate dependence of pressure-induced γ-form iPP was observed. When the shear rate was below 3.7 s−1, the pressure-induced γ-form dominated and the shear flow slightly facilitated formation of γ-form, owing to the enhanced nucleation rate. Unexpectedly, above 3.7 s−1, the shear flow was unfavorable for γ-form growth, because the molecular orientation induced by shear flow restrained the growth of γ-form crystals. Even under a pressure of 100 MP, a flow field with a shear rate above 9.1 s−1 could entirely suppress the γ-form. Moreover, we did not observe any trace of the β-form in the obtained iPP that is generally generated under shear flow alone. These interesting results can be understood on the basis of a combination of pressure-induced γ-form crystals and flow-induced crystallization (FIC), and undoubtedly help to manipulate the inner structure and thus enhance the performance of final iPP products.