diff --git a/tianshou/highlevel/config.py b/tianshou/highlevel/config.py
index bca77e0..02094bc 100644
--- a/tianshou/highlevel/config.py
+++ b/tianshou/highlevel/config.py
@@ -1,3 +1,4 @@
+import multiprocessing
 from dataclasses import dataclass
 
 from tianshou.utils.string import ToStringMixin
@@ -11,8 +12,9 @@ class SamplingConfig(ToStringMixin):
     num_epochs: int = 100
     step_per_epoch: int = 30000
     batch_size: int = 64
-    num_train_envs: int = 64
-    num_test_envs: int = 10
+    num_train_envs: int = -1
+    """the number of training environments to use. If set to -1, use number of CPUs/threads."""
+    num_test_envs: int = 1
     buffer_size: int = 4096
     step_per_collect: int = 2048
     repeat_per_collect: int | None = 10
@@ -27,3 +29,7 @@ class SamplingConfig(ToStringMixin):
     replay_buffer_ignore_obs_next: bool = False
     replay_buffer_save_only_last_obs: bool = False
     replay_buffer_stack_num: int = 1
+
+    def __post_init__(self) -> None:
+        if self.num_train_envs == -1:
+            self.num_train_envs = multiprocessing.cpu_count()