Objective: To observe changes in the growth of fluorescence-labelled tumour cells in nude mice using small animal in vivo imaging technology and to compare the anti-tumour effects of the administration of bevacizumab monoclonal antibodies combined with chemotherapy at different time sequences. Materials and Methods: Different time sequences of administration of bevacizumab monoclonal antibodies combined with the 5-fluorouracil and cisplatin (FP) chemotherapy regimen were used for intervention treatment of tumour growth in a subcutaneous xenograft model of human gastric cancer in nude mice. Tumour growth, that is, tumour volume, was evaluated with the changes in fluorescence signal strength and the inhibition rate. Results: Compared with the control group (normal saline), experimental groups had a certain inhibition rate, while the tumour inhibition rate in the group with a bevacizumab treatment for 24 h followed by the FP chemotherapy regimen was the highest (68.42%). Moreover, the fluorescence signal strength changed significantly in all of the experimental groups. At the 3rd week of bevacizumab administration, the fluorescence signal value in the group with a bevacizumab treatment for 24 h followed by the FP chemotherapy regimen was the lowest, indicating this is the best treatment out of five groups. Conclusion: Bevacizumab monoclonal antibodies combined with chemotherapy had synergistic effects. The small animal in vivo imaging system could dynamically obtain long and short diameters of tumours and their fluorescence signal values; compared with traditional methods that calculate tumour inhibition rates by weighing tumours, this method was more sensitive and more objective for drug evaluation.