Abstract: The paper aims to explore and screen higher efficient chemicals for inhibiting mycelium growth, conidia germination and protecting inoculation on excised twigs in vitro to Valsa mali, and to obtain environmentally friendly pesticides with good control effect, so as to provide theoretical basis for further prevention of apple tree canker in production. The inhibitory effect of mycelium growth, conidia germination and protective effect on excised twigs of five different chemicals were determined by the method of mycelium growth, conidia germination and scald inoculation on shoots in vitro. The results showed that difenoconazole had the highest activity for inhibiting mycelium growth and its EC₅₀ was 0.0163 μg/mL, followed by Propiconazole and tebuconazole with EC₅₀ value of 0.0224 and 0.0994 μg/mL. Alginate had the lowest activity for inhibiting mycelium growth and its EC₅₀ was 81.630 μg/mL. Difenoconazole had the highest activity for inhibiting conidia germination among all the tested chemicals, and its EC₅₀ was 0.0061 μg/mL. Propiconazole and tebuconazole took the second and the third place with EC₅₀ value of 0.0064 and 0.0390 μg/mL. Alginate had the lowest effect on inhibiting conidia germination and its EC₅₀ was 15.3820 μg/mL. The protective measures for protecting inoculation on excised twigs showed that alginate had the highest protection effect on shoot growth with the smallest scar expansion area of all, which was only 7.2% of that of CK; followed by Junduqing and tebuconazole, whose scar expansion area was 32.3% and 45.9% of that of CK, respectively. Propiconazole had the lowest protection effect on the shoot growth, its scar expansion area reached 59.8% of that of CK, and was the biggest of all chemicals tested. Difenoconazole was screened as the best chemical for inhibiting mycelium growth and conidia germination of Valsa mali. Alginate was screened as the best chemical for protecting shoot growth after inoculated with the pathogen of Valsa mali.