diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 78a00359bde3..9d830ab4e302 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -332,9 +332,25 @@ static void __init bootcmdline_init(char **cmdline_p)
 			strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
 
 		strlcat(boot_command_line, init_command_line, COMMAND_LINE_SIZE);
+		goto out;
 	}
 #endif
 
+	/*
+	 * Append built-in command line to the bootloader command line if
+	 * CONFIG_CMDLINE_EXTEND is enabled.
+	 */
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
+		strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+		strlcat(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+	}
+
+	/*
+	 * Use built-in command line if the bootloader command line is empty.
+	 */
+	if (IS_ENABLED(CONFIG_CMDLINE_BOOTLOADER) && !boot_command_line[0])
+		strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+
 out:
 	*cmdline_p = boot_command_line;
 }