ABSTRACT Drought along with high temperature around flowering is becoming more frequent to strongly influence maize production. However, the impacts of independent and combined drought and heat stress during this stage on subsequent grain filling have received limited attention. Here we investigated the response of grain development to three stresses (drought, heat and combined drought and heat stresses (DS, HS, DHS)) around flowering in ponds covered with a rain shelter in field. In additional, some grains were incubated in laboratory after pollination. Compared with control treatment, the decreased rate of grain weight was in the order of HS≤DS≤DHS in both experiments. In field, grain weight was decreased by 5-11% in stresses. The leaf senescence was accelerated together with decreased photosynthesis rate. Grain weight was still reduced largely in stresses with sufficient source supply in laboratory, which implicated a subsequent sink (grain) limit by early stresses. This mainly resulted from the disturbed carbohydrate metabolism and starch synthesis such as the activities of surcose invertase, sucrose synthase, ADP Glc pyrophosphorylase and starch synthase at early grain filling stage. This study provided information on how to promote drought and heat tolerance hybrids and mitigated management strategy.