diff --git a/ObservationSim/SimSteps.py b/ObservationSim/SimSteps.py
index 5b7c8bf86d2f0b3c9d0f8789ae2fc9d7d525c665..ecb484e6494d6df249246fddea9d7b611844fa59 100644
--- a/ObservationSim/SimSteps.py
+++ b/ObservationSim/SimSteps.py
@@ -109,6 +109,25 @@ class SimSteps:
         return chip, filt, tel, pointing
 
     def add_sky_background(self, chip, filt, tel, pointing, catalog, obs_param):
+        if not hasattr(self, 'h_ext'):
+            _, _ = self.prepare_headers(chip=chip, pointing=pointing)
+        chip_wcs = galsim.FitsWCS(header = self.h_ext)
+
+        if "flat_level" not in obs_param or "flat_level_filt" not in obs_param:
+            chip, filt, tel, pointing = self.add_sky_background_sci(chip, filt, tel, pointing, catalog, obs_param)
+        else:
+            if obs_param.get('flat_level') is None or obs_param.get('flat_level_filt')is None:
+                chip, filt, tel, pointing = self.add_sky_background_sci(chip, filt, tel, pointing, catalog, obs_param)
+            else:
+                chip, filt, tel, pointing = self.add_sky_flat_calibration(chip, filt, tel, pointing, catalog, obs_param)
+
+    chip, filt, tel, pointing = self.add_sky_background_sci(chip, filt, tel, pointing, catalog, obs_param)
+        
+        return chip, filt, tel, pointing
+
+
+
+    def add_sky_background_sci(self, chip, filt, tel, pointing, catalog, obs_param):
         flat_normal = np.ones_like(chip.img.array)
         if obs_param["flat_fielding"] == True:
             flat_normal = flat_normal * chip.flat_img.array / np.mean(chip.flat_img.array)
@@ -524,5 +543,5 @@ SIM_STEP_TYPES = {
     "gain": "apply_gain",
     "quantization_and_output": "quantization_and_output",
     "led_calib_model":"add_LED_Flat",
-    "sky_flatField":"add_sky_flat_calibration",
+    # "sky_flatField":"add_sky_flat_calibration",
 }
\ No newline at end of file
diff --git a/config/obs_config_Calibration.yaml b/config/obs_config_Calibration.yaml
index 99847ee21c9df034428663039003d2cb4169c0f9..933c6e09d65f493ffb374e927d62799156bfb1f0 100644
--- a/config/obs_config_Calibration.yaml
+++ b/config/obs_config_Calibration.yaml
@@ -24,12 +24,19 @@ call_sequence:
     LED_TYPE: ['LED5']
     LED_TIME: [1.]
   
-  sky_flatField:
+
+  # flat_level: set the total skybackground value (e-) in the exptime,if none,set null, or delete the key
+  # flat_level_filt: the vale of "flat_level" is in the filter "flat_level_filt", can set NUV, u, g, r, i, z, y, if 
+  # none,set null,or delete the key
+
+  sky_background:
     exptime: 150. # [s]
     shutter_effect: YES
     flat_fielding: YES
+    enable_straylight_model: YES
     flat_level: 20000
     flat_level_filt: g
+
   # Apply PRNU to accumulated photons
   PRNU_effect: {}
   # Accumulate photons caused by cosmic rays
diff --git a/config/obs_config_SCI_WIDE_phot.yaml b/config/obs_config_SCI_WIDE_phot.yaml
index df6203a8a0911acdb25ccbaf65d7b43e31918ca1..428363715e0bdf70b1f132d6dfd0fcade3f6db28 100644
--- a/config/obs_config_SCI_WIDE_phot.yaml
+++ b/config/obs_config_SCI_WIDE_phot.yaml
@@ -23,11 +23,16 @@ call_sequence:
     flat_fielding: YES
     field_dist: YES
   # Accumulate fluxes from sky background
+  # flat_level: set the total skybackground value (e-) in the exptime,if none,set null, or delete the key
+  # flat_level_filt: the vale of "flat_level" is in the filter "flat_level_filt", can set NUV, u, g, r, i, z, y, if 
+  # none,set null,or delete the key
   sky_background:
     exptime: 150. # [s]
     shutter_effect: YES
     flat_fielding: YES
     enable_straylight_model: YES
+    flat_level: null
+    flat_level_filt: null
   # Apply PRNU to accumulated photons
   PRNU_effect: {}
   # Accumulate photons caused by cosmic rays