diff --git a/README.md b/README.md
index f8902dd..d6fa0c9 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,10 @@
 
 BL602 serial flasher
 
+blflash is written in rust. It requires the latest environment of rust, which
+you can get via running 'rustup update'. You can build blflash by running
+'cargo build'.
+
 Inspired by https://github.com/esp-rs/espflash, https://github.com/bouffalolab/BLOpenFlasher
 
 ISP documentation: https://github.com/bouffalolab/bl_docs/tree/main/BL602_ISP